// ================== PLANNER ZHL-16B/C + GF (dt=1s, PH2O=0.0627) ==================
$w.onReady(() => {
    $w('#planBtn').onClick(() => {
        const { pn, pe } = runTissuesWithDescent(); // Step 1: discesa + fondo
        showCeilingInfo(pn, pe); //     : ceiling iniziale + prima tappa
        runDecoPlan(pn, pe); // Step 3: risalita a prima tappa + piano deco + consumi + END/Density + CNS
    });
});

// === Lettura modello B/C dal RadioGroup ===
function currentModel() {
    try {
        const el = $w('#radioGroup1');
        if (el && typeof el.value === 'string') {
            const v = el.value.trim().toUpperCase();
            return (v === 'C') ? 'C' : 'B';
        }
    } catch (e) {}
    return 'B';
}

// --- Parametri numerici / fine tuning  (arrotondamenti così sono più restrittivo in profondità e più perimissivo in superficie) ---
const STEP_SEC = 1;
const SHALLOW_THRESHOLD = 15;
const CEIL_EPS_DEEP = -0.012;
const CEIL_EPS_SHALLOW = +0.001;
const ROUNDING = "floor";
const FIRST_STOP_EPS = 0.03;

// --- Stile output ---
const USE_HTML_COLORS = true;
const COLOR_BASE_TEXT = "#ffffff";
const COLOR_DIM_TEXT = "#9aa0a6";
const HILITE_BG = "#64ffda";
const HILITE_FG = "#00332b";

// ==================== Coefficienti ZHL-16B / ZHL-16C ==============================
function getCoefficients() {
    const model = currentModel();
    if (model === "B") {
        return {
            halftimen2: [4.0, 8.0, 12.5, 18.5, 27.0, 38.3, 54.3, 77.0, 109.0, 146.0, 187.0, 239.0, 305.0, 390.0, 498.0, 635.0],
            halftimehe: [1.5, 3.0, 4.7, 7.0, 10.2, 14.5, 20.5, 29.1, 41.1, 55.1, 70.6, 90.2, 115.1, 147.2, 187.9, 239.6],
            n2a: [1.2599, 1.0, 0.8618, 0.7562, 0.6667, 0.5933, 0.5282, 0.4701, 0.4187, 0.3798, 0.3497, 0.3223, 0.2971, 0.2737, 0.2523, 0.2327],
            n2b: [0.505, 0.6514, 0.7222, 0.7725, 0.8125, 0.8434, 0.8693, 0.891, 0.9092, 0.9222, 0.9319, 0.9403, 0.9477, 0.9544, 0.9602, 0.9653],
            hea: [1.7435, 1.3838, 1.1925, 1.0465, 0.9226, 0.8211, 0.7309, 0.6506, 0.5794, 0.5256, 0.484, 0.446, 0.4112, 0.3788, 0.3492, 0.322],
            heb: [0.1911, 0.4295, 0.5446, 0.6265, 0.6917, 0.742, 0.7841, 0.8195, 0.8491, 0.8703, 0.886, 0.8997, 0.9118, 0.9226, 0.9321, 0.9404]
        };
    } else {
        return {
            halftimen2: [4.0, 8.0, 12.5, 18.5, 27.0, 38.3, 54.3, 77.0, 109.0, 146.0, 187.0, 239.0, 305.0, 390.0, 498.0, 635.0],
            halftimehe: [1.51, 3.02, 4.72, 6.99, 10.21, 14.48, 20.53, 29.11, 41.20, 55.19, 70.69, 90.34, 115.29, 147.42, 188.24, 240.03],
            n2a: [1.1696, 1.0, 0.8618, 0.7562, 0.6667, 0.5933, 0.5282, 0.4701, 0.4187, 0.3798, 0.3497, 0.3223, 0.2971, 0.2737, 0.2523, 0.2327],
            n2b: [0.5578, 0.6514, 0.7222, 0.7825, 0.8126, 0.8434, 0.8693, 0.8910, 0.9092, 0.9222, 0.9319, 0.9403, 0.9477, 0.9544, 0.9602, 0.9653],
            hea: [1.6189, 1.3830, 1.1919, 1.0458, 0.9220, 0.8205, 0.7305, 0.6502, 0.5950, 0.5545, 0.5333, 0.5189, 0.5181, 0.5176, 0.5172, 0.5119],
            heb: [0.4770, 0.5747, 0.6527, 0.7223, 0.7582, 0.7957, 0.8279, 0.8553, 0.8757, 0.8903, 0.8997, 0.9073, 0.9122, 0.9171, 0.9217, 0.9267]
        };
    }
}

// ===================== ceilingGF  =====================
function ceilingGF(pnArr, peArr, GF) {
    const { n2a, n2b, hea, heb } = getCoefficients();
    let cmax = 0;
    for (let i = 0; i < 16; i++) {
        const PN2 = pnArr[i],
            PHe = peArr[i],
            Pt = PN2 + PHe;
        if (Pt <= 0) continue;
        const A = ((n2a[i] * PN2) + (hea[i] * PHe)) / Pt;
        const B = ((n2b[i] * PN2) + (heb[i] * PHe)) / Pt;
        const denom = GF - (GF * B) + B; // B + GF*(1-B)
        const Pmin = (Pt - A * GF) * (B / Math.max(denom, 1e-9));
        if (Pmin > cmax) cmax = Pmin;
    }
    return cmax;
}

// ===================== SATURAZIONE: DISCESA + FONDO ===============================
function runTissuesWithDescent() {
    const { halftimen2, halftimehe } = getCoefficients();
    const { depth_m, bottomMin, descRate } = getDiveParams();
    const gases = getGases();
    const PH2O = 0.0627;

    // iniziale (aria a 1 bar)
    const PN2_0 = 0.7902 * (1.0 - PH2O);
    let pn = Array(16).fill(PN2_0);
    let pe = Array(16).fill(0);

    const kN2 = halftimen2.map(ht => Math.log(2) / (ht * 60));
    const kHe = halftimehe.map(ht => Math.log(2) / (ht * 60));

    // DISCESA su gas di fondo
    integrateTravelTissues(pn, pe, kN2, kHe, gases[0], 0, depth_m, descRate, PH2O);

    // FONDO su gas di fondo
    const Pamb = 1 + depth_m / 10;
    const PiN2 = gases[0].FN2 * (Pamb - PH2O);
    const PiHe = gases[0].FHe * (Pamb - PH2O);
    const totalSec = Math.round(bottomMin * 60);
    for (let t = 0; t < totalSec; t += STEP_SEC) {
        for (let i = 0; i < 16; i++) {
            pn[i] += (PiN2 - pn[i]) * (1 - Math.exp(-kN2[i] * STEP_SEC));
            pe[i] += (PiHe - pe[i]) * (1 - Math.exp(-kHe[i] * STEP_SEC));
        }
    }

    // (debug )
    let lines = [];
    lines.push(`\n\n Nerd things:\nTissue saturation after descent + ${bottomMin} min @ ${depth_m} m\n`);
    lines.push("Idx | PN₂ (bar) | PHe (bar) | Ptot (bar)");
    for (let i = 0; i < 16; i++) {
        lines.push(`${pad2(i+1)} | ${r3(pn[i])} | ${r3(pe[i])} | ${r3(pn[i]+pe[i])}`);
    }
    $w('#text27').text = lines.join("\n");

    return { pn, pe };
}

// integrazione tessuti durante spostamento verticale a gas fisso
function integrateTravelTissues(pn, pe, kN2, kHe, gas, fromDepth, toDepth, rate_m_per_min, PH2O) {
    if (!isFinite(fromDepth) || !isFinite(toDepth) || rate_m_per_min <= 0) return;
    const delta = toDepth - fromDepth;
    const dist = Math.abs(delta);
    if (dist < 1e-6) return;
    const steps = Math.max(1, Math.ceil(dist));
    const stepM = delta / steps;
    const dtMin = Math.abs(stepM) / rate_m_per_min;
    const dtSec = dtMin * 60;

    for (let iStep = 0; iStep < steps; iStep++) {
        const midDepth = fromDepth + (iStep + 0.5) * stepM;
        const Pamb = 1 + Math.max(0, midDepth) / 10;
        const PiN2 = gas.FN2 * (Pamb - PH2O);
        const PiHe = gas.FHe * (Pamb - PH2O);
        for (let i = 0; i < 16; i++) {
            pn[i] += (PiN2 - pn[i]) * (1 - Math.exp(-kN2[i] * dtSec));
            pe[i] += (PiHe - pe[i]) * (1 - Math.exp(-kHe[i] * dtSec));
        }
    }
}

// =============== STEP 2 — Ceiling iniziale + prima tappa ===========================
function showCeilingInfo(pn, pe) {
    const depth_m = n('#depth');
    const pressione = 1 + depth_m / 10;
    const gflow = n('#gfLow') / 100;
    const gfhi = n('#gfHigh') / 100;

    // GF info
    let GFm = (gfhi - gflow) / ((pressione - 1) * 10);
    let GF = gfhi - GFm * ((pressione - 1) * 10);
    let gffinal = Math.min(Math.max(GF, gflow), gfhi);

    // Prima tappa (semper arrotondata a SALIRE al multiplo di 3 m)
    const ceiling0_raw = ceilingGF(pn, pe, gflow);
    const ceiling0 = ceiling0_raw + FIRST_STOP_EPS;
    let primatappamax = Math.ceil(((ceiling0 - 1) * 10) / 3) * 3;
    if (primatappamax < 3) primatappamax = 3;

    let lines = [];
    lines.push(`Model: ZHL-16${currentModel()} + GF ${Math.round(gflow*100)}/${Math.round(gfhi*100)}`);
    lines.push(`GF (at current Pamb): ${gffinal.toFixed(2)}`);
    lines.push(`Ceiling: ${(((ceiling0_raw-1)*10)).toFixed(1)} m`);
    lines.push(`First stop depth: ${primatappamax} m`);
    $w('#text29').text = lines.join("\n");
}

// =============== PIANO DECO + RISALITA ALLA PRIMA TAPPA ===========================
function runDecoPlan(pn, pe) {
    const gflow = n('#gfLow') / 100,
        gfhi = n('#gfHigh') / 100;
    const gases = getGases();
    const { halftimen2, halftimehe } = getCoefficients();
    const PH2O = 0.0627;
    const { depth_m, ascRate } = getDiveParams();

    const kN2 = halftimen2.map(ht => Math.log(2) / (ht * 60));
    const kHe = halftimehe.map(ht => Math.log(2) / (ht * 60));

    function pickBestGas(depthM) {
        const Pamb = 1 + depthM / 10;
        let usable = gases.filter(g => isFinite(g.switchDepth) && depthM <= g.switchDepth);
        usable = usable.filter(g => g.FO2 * Pamb <= g.ppo2lim + 1e-6);
        if (!usable.length) return gases[0];
        usable.sort((a, b) => b.FO2 - a.FO2);
        return usable[0];
    }

    // copie tessuti
    let decopn = pn.slice(),
        decope = pe.slice();

    // prima tappa da ceiling con GF_low
    const ceiling0_raw = ceilingGF(decopn, decope, gflow);
    const ceiling0 = ceiling0_raw + FIRST_STOP_EPS;
    let primatappamax = Math.ceil(((ceiling0 - 1) * 10) / 3) * 3;
    if (primatappamax < 3) primatappamax = 3;

    // integra RISALITA fondo -> prima tappa con gas dinamico (coerente col planner)
    {
        const from = depth_m,
            to = primatappamax;
        if (ascRate > 0 && from > to) {
            const delta = from - to;
            const steps = Math.max(1, Math.ceil(delta));
            for (let i = 0; i < steps; i++) {
                const d1 = from - i;
                const d2 = from - (i + 1);
                const mid = (d1 + d2) / 2;
                const gas = pickBestGas(Math.max(0, mid));
                integrateTravelTissues(decopn, decope, kN2, kHe, gas, d1, d2, ascRate, PH2O);
            }
        }
    }

    // retta GF
    const GFmdeco = (gfhi - gflow) / primatappamax;

    let counterstep = primatappamax;
    let stops = [];

    while (counterstep > 0) {
        let GF = gfhi - GFmdeco * counterstep;
        if (GF < gflow) GF = gflow;
        if (GF > gfhi) GF = gfhi;

        const gasNow = pickBestGas(counterstep);
        const PambStop = 1 + counterstep / 10;
        const PiN2 = gasNow.FN2 * (PambStop - PH2O);
        const PiHe = gasNow.FHe * (PambStop - PH2O);

        let holdSec = 0;
        let decoceiling = ceilingGF(decopn, decope, GF);
        const nextPamb = PambStop - 0.3;
        const eps = (counterstep <= SHALLOW_THRESHOLD) ? CEIL_EPS_SHALLOW : CEIL_EPS_DEEP;

        while (decoceiling > nextPamb + eps) {
            for (let i = 0; i < 16; i++) {
                decopn[i] += (PiN2 - decopn[i]) * (1 - Math.exp(-kN2[i] * STEP_SEC));
                decope[i] += (PiHe - decope[i]) * (1 - Math.exp(-kHe[i] * STEP_SEC));
            }
            holdSec += STEP_SEC;
            decoceiling = ceilingGF(decopn, decope, GF);
        }

        const holdMin = (ROUNDING === "floor") ? Math.floor(holdSec / 60) : Math.round(holdSec / 60);
        if (holdMin > 0) {
            stops.push({ depth: counterstep, time: holdMin, GF, ceiling: decoceiling, gas: gasNow });
        }
        counterstep -= 3;
    }

    // ---- Consumi ----
    const usage = computeGasUsage(stops, gases);

    // ---- Runtime cumulativo (min) ----
    const { depth_m: D, bottomMin: BT, descRate, ascRate: AR } = getDiveParams();
    let runtimeMin = 0;
    if (isFinite(D) && descRate > 0) runtimeMin += D / descRate; // discesa
    if (isFinite(BT) && BT > 0) runtimeMin += BT; // fondo
    let rtLeaveBottom = runtimeMin; // runtime quando si lascia il fondo
    if (stops.length > 0 && AR > 0) runtimeMin += (D - stops[0].depth) / AR; // alla 1ª tappa
    const firstStopRt = runtimeMin;

    for (let i = 0; i < stops.length; i++) {
        const s = stops[i];
        runtimeMin += s.time;
        s.runtime = runtimeMin;
        if (i < stops.length - 1 && AR > 0) {
            const nextDepth = stops[i + 1].depth;
            runtimeMin += (s.depth - nextDepth) / AR;
        }
    }

    // ---- END & Gas Density (solo gas di fondo) ----
    const infoBottom = bottomGasInfo(gases[0], D);

    // ---- CNS% totale (NOAA) su discesa, fondo, risalite, soste) ----
    const cnsTotal = computeCNSPercent(stops, gases);

    // ===== Output piano (allineato, depth/time evidenziati) =====
    const DEP_W = 5,
        TIME_W = 6,
        RT_W = 6,
        GAS_W = 18,
        PPO2_W = 5;

    let rows = [];
    rows.push(spanBase(`PLAN — Single OC (ZHL-16${currentModel()} + GF ${Math.round(gflow*100)}/${Math.round(gfhi*100)})`, COLOR_BASE_TEXT));
    rows.push(spanDim(`(ppO₂ shown at stop depth)\n`, COLOR_DIM_TEXT));
    rows.push(""); // riga vuota

    // RIEPILOGO GAS DI FONDO: END & Densità
    rows.push(spanBase(`Bottom gas: ${gasDisplay(gases[0]).label}`, COLOR_BASE_TEXT));
    rows.push(spanDim(`\nEND @ ${D} m: ${infoBottom.ENDm.toFixed(0)} m | Gas density @ ${D} m: ${infoBottom.density_gL.toFixed(2)} g/L\n\n\n`, COLOR_DIM_TEXT));
    rows.push(""); // riga vuota

    // Riga "leave bottom" + runtime fino alla 1ª tappa
    if (stops.length) {
        rows.push(
            spanDim(`Leave bottom (${Math.round(rtLeaveBottom)})`, COLOR_DIM_TEXT) +
            spanBase(`\n → ascend to first stop @ `, COLOR_BASE_TEXT) +
            spanHilite(rcol(`${stops[0].depth} m`, DEP_W)) +
            spanBase(`    `, COLOR_BASE_TEXT) +
            spanDim(`(${Math.round(firstStopRt)})`, COLOR_DIM_TEXT)
        );
    }

    // Soste
    for (const s of stops) {
        const depthStr = `${s.depth} m`;
        const timeStr = `${s.time} min`;
        const PambStop = 1 + s.depth / 10;
        const ppO2 = (s.gas.FO2 * PambStop).toFixed(2);
        const runStr = `(${Math.round(s.runtime)})`;
        const gdisp = gasDisplay(s.gas);
        const gasStr = gdisp.label;

        const line =
            spanBase("\nStop @ ", COLOR_BASE_TEXT) +
            spanHilite(rcol(depthStr, DEP_W)) + spanBase("  ", COLOR_BASE_TEXT) +
            spanHilite(rcol(timeStr, TIME_W)) + spanBase("  ", COLOR_BASE_TEXT) +
            spanDim(rcol(runStr, RT_W), COLOR_DIM_TEXT) + spanBase("  ", COLOR_BASE_TEXT) +
            spanBase("--> ", COLOR_BASE_TEXT) +
            spanDim(lcol(gasStr, GAS_W), COLOR_DIM_TEXT) + spanBase("  ", COLOR_BASE_TEXT) +
            spanDim(`ppO₂ ${rcol(ppO2, PPO2_W)}`, COLOR_DIM_TEXT);

        rows.push(line);
    }

    // Consumi
    rows.push('\n' + spanBase('\nGas usage (surface liters):\n', COLOR_BASE_TEXT));
    let totalNL = 0;
    for (const it of usage) {
        totalNL += it.liters;
        const lbl = lcol(it.label, 18);
        const val = rcol(Math.round(it.liters).toString(), 8);
        rows.push(spanDim(`• ${lbl}  ${val} NL\n`, COLOR_DIM_TEXT));
    }
    rows.push(spanDim(`Total${' '.repeat(17)}${rcol(Math.round(totalNL).toString(), 8)} NL\n`, COLOR_DIM_TEXT));

    // CNS
    rows.push('');
    rows.push(spanBase(`\nCNS total: ${cnsTotal.toFixed(0)}%\n\n\n\n\n`, COLOR_BASE_TEXT));

    const html =
        `<pre style="
      margin:0; white-space:pre-wrap;
      font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, 'Courier New', monospace;
      font-size:14px; line-height:1.4; color:${COLOR_BASE_TEXT};
    ">` + rows.join("") + `</pre>`;

    if ($w('#planText').html !== undefined) $w('#planText').html = html;
    else if ($w('#planText').value !== undefined) $w('#planText').value = html;
    else $w('#planText').text = rows.map(stripTags).join("\n");

    // --- Snapshot tessuti immediatamente a superficie (Air 21/79) ---
    function renderSurfaceTissues(decopn, decope, lastStopDepth, ascRate, kN2, kHe, PH2O) {
        let pnS = decopn.slice();
        let peS = decope.slice();

        // Risalita ultima sosta -> superficie con aria (21/79)
        if (isFinite(lastStopDepth) && lastStopDepth > 0 && ascRate > 0) {
            const air = { FO2: 0.21, FHe: 0.00, FN2: 0.79 };
            integrateTravelTissues(pnS, peS, kN2, kHe, air, lastStopDepth, 0, ascRate, PH2O);
        }

        // Snapshot NOW @ surface
        let lines = [];
        lines.push("\n\n\nTissue saturation @ surface (Air 21/79)\n");
        lines.push("Idx | PN₂ (bar) | PHe (bar) | Ptot (bar)");
        for (let i = 0; i < 16; i++) {
            const PN2 = pnS[i];
            const PHe = peS[i];
            const Ptot = PN2 + PHe;
            lines.push(`${pad2(i+1)} | ${r3(PN2)} | ${r3(PHe)} | ${r3(Ptot)}`);
        }

        if ($w('#text37').text !== undefined) {
            $w('#text37').text = lines.join("\n");
        }
    }
    // --- Snapshot tessuti a superficie ---
    const lastStopDepth = (stops.length ? stops[stops.length - 1].depth : 0);
    renderSurfaceTissues(decopn, decope, lastStopDepth, AR, kN2, kHe, PH2O);

    return stops;
}

// ================= GAS (robusto a campi vuoti / EAN/O2) ============================
function getGases() {
    function _raw(id) { return String($w(id).value || '').trim(); }

    function _num(id) { const s = _raw(id).replace(',', '.'); const v = Number(s); return isFinite(v) ? v : NaN; }

    function _pct(id, def = 0) { const v = _num(id); return isFinite(v) ? v / 100 : def; }

    // usa #maxppo2 per TUTTE le miscele
    const maxppo2 = _num('#maxppo2');

    let gases = [
        { name: "Bottom", FO2: _pct('#o20', 0), FHe: _pct('#he0', 0), ppo2lim: maxppo2 },
        { name: "Deco1", FO2: _pct('#o21', 0), FHe: _pct('#he1', 0), ppo2lim: maxppo2 },
        { name: "Deco2", FO2: _pct('#o22', 0), FHe: _pct('#he2', 0), ppo2lim: maxppo2 },
        { name: "Deco3", FO2: _pct('#o23', 0), FHe: _pct('#he3', 0), ppo2lim: maxppo2 },
        { name: "Deco4", FO2: _pct('#o24', 0), FHe: _pct('#he4', 0), ppo2lim: maxppo2 }
    ];

    gases.forEach(g => {
        g.FO2 = Math.min(1, Math.max(0, isFinite(g.FO2) ? g.FO2 : 0));
        g.FHe = Math.min(1, Math.max(0, isFinite(g.FHe) ? g.FHe : 0));
        let sum = g.FO2 + g.FHe;
        if (sum > 1) {
            g.FO2 = g.FO2 / sum;
            g.FHe = g.FHe / sum;
        }
        g.FN2 = 1 - g.FO2 - g.FHe;

        if (g.FO2 > 0 && isFinite(g.ppo2lim) && g.ppo2lim > 0) {
            const PambMax = g.ppo2lim / g.FO2;
            g.switchDepth = (PambMax - 1) * 10;
        } else {
            g.switchDepth = NaN;
        }
    });
    return gases.filter(g => isFinite(g.FN2));
}

// ===================== GAS USAGE (surface liters) =================================
function getDiveParams() {
    const depth_m = n('#depth');
    const bottomMin = n('#bottomTime');
    let descRate = n('#descRate');
    let ascRate = n('#ascRate');
    const rmv = n('#rmv');
    if (!isFinite(descRate) || descRate <= 0) descRate = 20;
    if (!isFinite(ascRate) || ascRate <= 0) ascRate = 10;
    return { depth_m, bottomMin, descRate, ascRate, rmv };
}

function gasAtDepth(gases, depthM) {
    const Pamb = 1 + depthM / 10;
    let usable = gases.filter(g => isFinite(g.switchDepth) && depthM <= g.switchDepth);
    usable = usable.filter(g => g.FO2 * Pamb <= g.ppo2lim + 1e-6);
    if (!usable.length) return gases[0];
    usable.sort((a, b) => b.FO2 - a.FO2);
    return usable[0];
}

function integrateTravel(gases, fromDepth, toDepth, rate_m_per_min, rmv, accum) {
    if (!isFinite(fromDepth) || !isFinite(toDepth) || rate_m_per_min <= 0) return;
    const delta = toDepth - fromDepth,
        dist = Math.abs(delta);
    if (dist < 1e-6) return;
    const steps = Math.max(1, Math.ceil(dist));
    const stepM = delta / steps;
    const dtMin = Math.abs(stepM) / rate_m_per_min;

    for (let i = 0; i < steps; i++) {
        const midDepth = fromDepth + (i + 0.5) * stepM;
        const Pamb = 1 + Math.max(0, midDepth) / 10;
        const gas = gasAtDepth(gases, Math.max(0, midDepth));
        const key = gasKey(gas);
        const consSL   = rmv * Pamb * dtMin;
        accum[key] = (accum[key] || 0) + consSL;
    }
}

function integrateHold(gases, depthM, minutes, rmv, accum) {
    if (minutes <= 0) return;
    const Pamb = 1 + depthM / 10;
    const gas = gasAtDepth(gases, depthM);
    const key = gasKey(gas);
    const cons = rmv * Pamb * minutes;
    accum[key] = (accum[key] || 0) + cons;
}

// --- integrazione consumi con GAS FORZATO (discesa e fondo) ---
function integrateTravelWithGas(gas, fromDepth, toDepth, rate_m_per_min, rmv, accum) {
    if (!isFinite(fromDepth) || !isFinite(toDepth) || rate_m_per_min <= 0) return;
    const delta = toDepth - fromDepth,
        dist = Math.abs(delta);
    if (dist < 1e-6) return;
    const steps = Math.max(1, Math.ceil(dist));
    const stepM = delta / steps;
    const dtMin = Math.abs(stepM) / rate_m_per_min;

    const key = gasKey(gas);
    for (let i = 0; i < steps; i++) {
        const midDepth = fromDepth + (i + 0.5) * stepM;
        const Pamb = 1 + Math.max(0, midDepth) / 10;
        const consSL = rmv * Pamb * dtMin;
        accum[key] = (accum[key] || 0) + consSL;
    }
}

function integrateHoldWithGas(gas, depthM, minutes, rmv, accum) {
    if (minutes <= 0) return;
    const Pamb = 1 + depthM / 10;
    const key = gasKey(gas);
    const cons = rmv * Pamb * minutes;
    accum[key] = (accum[key] || 0) + cons;
}

function gasKey(g) { return `${g.name}|${Math.round(g.FO2*100)}/${Math.round(g.FHe*100)}`; }

function gasLabelFromKey(k) {
    const [_, mix] = k.split('|');
    const [o2s, hes] = mix.split('/').map(Number);
    if (o2s === 21 && hes === 0) return 'Air';
    if (o2s === 100 && hes === 0) return 'Oxygen';
    if (hes > 0) return `Trimix ${o2s}/${hes}`;
    if (o2s > 21) return `Nitrox ${o2s}`;
    return `Gas ${mix}`;
}

function computeGasUsage(stops, gases) {
    const { depth_m, bottomMin, descRate, ascRate, rmv } = getDiveParams();
    const accum = {};
    const bottomGas = gases[0]; // forza la miscela di fondo

    // PRIMA: discesa su bottom gas
    integrateTravelWithGas(bottomGas, 0, depth_m, descRate, rmv, accum);

    // POI: fondo su bottom gas
    integrateHoldWithGas(bottomGas, depth_m, bottomMin, rmv, accum);

    // Risalita fino alla prima tappa: dinamico (switch appena è lecito)
    const firstStopDepth = (stops.length ? stops[0].depth : 3);
    integrateTravel(gases, depth_m, firstStopDepth, ascRate, rmv, accum);

    // Soste + risalite tra tappe: dinamico
    for (let i = 0; i < stops.length; i++) {
        const s = stops[i];
        integrateHold(gases, s.depth, s.time, rmv, accum);
        const nextDepth = (i < stops.length - 1) ? stops[i + 1].depth : 0;
        integrateTravel(gases, s.depth, nextDepth, ascRate, rmv, accum);
    }

    const items = Object.entries(accum).map(([k, liters]) => ({ key: k, label: gasLabelFromKey(k), liters }));
    items.sort((a, b) => a.label.localeCompare(b.label));
    return items;
}

// ===================== END & GAS DENSITY (gas di fondo) ===========================
// END (m) assumendo solo N2 come narcotico (O2 non narcotico): END = ((FN2/0.79)*(D+10))-10
function computeENDmeters(bottomGas, depth_m) {
    const FN2 = bottomGas.FN2;
    const Pamb = 1 + depth_m / 10;
    const END_ambient = (FN2 / 0.79) * Pamb; // equivalente air pressure
    return Math.max(0, (END_ambient - 1) * 10);
}

// densità mix @ 1 bar (kg/m^3) a ~20°C: He 0.1786, N2 1.2506, O2 1.331
function gasDensityAtDepth(bottomGas, depth_m) {
    const rhoHe = 0.1786,
        rhoN2 = 1.2506,
        rhoO2 = 1.3310;
    const rho1bar = bottomGas.FHe * rhoHe + bottomGas.FN2 * rhoN2 + bottomGas.FO2 * rhoO2; // kg/m3
    const Pamb = 1 + depth_m / 10;
    const rhoDepth = rho1bar * Pamb; // kg/m3
    return rhoDepth * 1.0; // kg/m3 -> kg/m3 (convertiamo dopo in g/L)
}

function bottomGasInfo(bottomGas, depth_m) {
    const ENDm = computeENDmeters(bottomGas, depth_m);
    const rho_kgm3 = gasDensityAtDepth(bottomGas, depth_m);
    const density_gL = rho_kgm3; // 1 kg/m3 = 1 g/L
    return { ENDm, density_gL };
}

// ===================== CNS NOAA ===================================================
// Tabella NOAA (minuti per 100% CNS) a vari ppO2 (bar). Linear interp. Sotto 0.5 bar = 0.
const NOAA_TABLE = [
    { pp: 1.6, min: 45 }, { pp: 1.5, min: 120 }, { pp: 1.4, min: 150 }, { pp: 1.3, min: 180 },
    { pp: 1.2, min: 210 }, { pp: 1.1, min: 240 }, { pp: 1.0, min: 300 }, { pp: 0.9, min: 360 },
    { pp: 0.8, min: 450 }, { pp: 0.7, min: 570 }, { pp: 0.6, min: 720 }, { pp: 0.5, min: 1440 }
];

function minutesFor100CNS(pp) {
    if (pp < 0.5) return Infinity;
    // clamp in range
    if (pp >= NOAA_TABLE[0].pp) return NOAA_TABLE[0].min;
    if (pp <= NOAA_TABLE[NOAA_TABLE.length - 1].pp) return NOAA_TABLE[NOAA_TABLE.length - 1].min;
    // linear interp between surrounding nodes
    for (let i = 0; i < NOAA_TABLE.length - 1; i++) {
        const a = NOAA_TABLE[i],
            b = NOAA_TABLE[i + 1];
        if (pp <= a.pp && pp >= b.pp) {
            const t = (pp - b.pp) / (a.pp - b.pp);
            return b.min + t * (a.min - b.min);
        }
    }
    return Infinity;
}

function cnsIncrement(pp, minutes) {
    const M = minutesFor100CNS(pp);
    if (!isFinite(M) || M === Infinity) return 0;
    return (minutes / M) * 100;
}
// calcolo CNS% integrando a step di 1 m durante discese/risalite + soste + fondo
function computeCNSPercent(stops, gases) {
    const { depth_m, bottomMin, descRate, ascRate } = getDiveParams();
    let cns = 0;

    // helper: CNS su travel (1 m per step)
    function cnsTravel(fromDepth, toDepth, rate_m_per_min) {
        if (!isFinite(fromDepth) || !isFinite(toDepth) || rate_m_per_min <= 0) return;
        const delta = toDepth - fromDepth,
            dist = Math.abs(delta);
        if (dist < 1e-6) return;
        const steps = Math.max(1, Math.ceil(dist));
        const stepM = delta / steps;
        const dtMin = Math.abs(stepM) / rate_m_per_min;
        for (let i = 0; i < steps; i++) {
            const midDepth = fromDepth + (i + 0.5) * stepM;
            const gas = gasAtDepth(gases, Math.max(0, midDepth));
            const ppO2 = gas.FO2 * (1 + Math.max(0, midDepth) / 10);
            cns += cnsIncrement(ppO2, dtMin);
        }
    }
    // helper: CNS su hold
    function cnsHold(depthM, minutes) {
        if (minutes <= 0) return;
        const gas = gasAtDepth(gases, depthM);
        const ppO2 = gas.FO2 * (1 + depthM / 10);
// ================== PLANNER ZHL-16B/C + GF (dt=1s, PH2O=0.0627) ==================
$w.onReady(() => {
    $w('#planBtn').onClick(() => {
        const { pn, pe } = runTissuesWithDescent(); // Step 1: discesa + fondo
        showCeilingInfo(pn, pe); //     : ceiling iniziale + prima tappa
        runDecoPlan(pn, pe); // Step 3: risalita a prima tappa + piano deco + consumi + END/Density + CNS
    });
});

// === Lettura modello B/C dal RadioGroup ===
function currentModel() {
    try {
        const el = $w('#radioGroup1');
        if (el && typeof el.value === 'string') {
            const v = el.value.trim().toUpperCase();
            return (v === 'C') ? 'C' : 'B';
        }
    } catch (e) {}
    return 'B';
}

// --- Parametri numerici / fine tuning  (arrotondamenti così sono più restrittivo in profondità e più perimissivo in superficie) ---
const STEP_SEC = 1;
const SHALLOW_THRESHOLD = 15;
const CEIL_EPS_DEEP = -0.012;
const CEIL_EPS_SHALLOW = +0.001;
const ROUNDING = "floor";
const FIRST_STOP_EPS = 0.03;

// --- Stile output ---
const USE_HTML_COLORS = true;
const COLOR_BASE_TEXT = "#ffffff";
const COLOR_DIM_TEXT = "#9aa0a6";
const HILITE_BG = "#64ffda";
const HILITE_FG = "#00332b";

// ==================== Coefficienti ZHL-16B / ZHL-16C ==============================
function getCoefficients() {
    const model = currentModel();
    if (model === "B") {
        return {
            halftimen2: [4.0, 8.0, 12.5, 18.5, 27.0, 38.3, 54.3, 77.0, 109.0, 146.0, 187.0, 239.0, 305.0, 390.0, 498.0, 635.0],
            halftimehe: [1.5, 3.0, 4.7, 7.0, 10.2, 14.5, 20.5, 29.1, 41.1, 55.1, 70.6, 90.2, 115.1, 147.2, 187.9, 239.6],
            n2a: [1.2599, 1.0, 0.8618, 0.7562, 0.6667, 0.5933, 0.5282, 0.4701, 0.4187, 0.3798, 0.3497, 0.3223, 0.2971, 0.2737, 0.2523, 0.2327],
            n2b: [0.505, 0.6514, 0.7222, 0.7725, 0.8125, 0.8434, 0.8693, 0.891, 0.9092, 0.9222, 0.9319, 0.9403, 0.9477, 0.9544, 0.9602, 0.9653],
            hea: [1.7435, 1.3838, 1.1925, 1.0465, 0.9226, 0.8211, 0.7309, 0.6506, 0.5794, 0.5256, 0.484, 0.446, 0.4112, 0.3788, 0.3492, 0.322],
            heb: [0.1911, 0.4295, 0.5446, 0.6265, 0.6917, 0.742, 0.7841, 0.8195, 0.8491, 0.8703, 0.886, 0.8997, 0.9118, 0.9226, 0.9321, 0.9404]
        };
    } else {
        return {
            halftimen2: [4.0, 8.0, 12.5, 18.5, 27.0, 38.3, 54.3, 77.0, 109.0, 146.0, 187.0, 239.0, 305.0, 390.0, 498.0, 635.0],
            halftimehe: [1.51, 3.02, 4.72, 6.99, 10.21, 14.48, 20.53, 29.11, 41.20, 55.19, 70.69, 90.34, 115.29, 147.42, 188.24, 240.03],
            n2a: [1.1696, 1.0, 0.8618, 0.7562, 0.6667, 0.5933, 0.5282, 0.4701, 0.4187, 0.3798, 0.3497, 0.3223, 0.2971, 0.2737, 0.2523, 0.2327],
            n2b: [0.5578, 0.6514, 0.7222, 0.7825, 0.8126, 0.8434, 0.8693, 0.8910, 0.9092, 0.9222, 0.9319, 0.9403, 0.9477, 0.9544, 0.9602, 0.9653],
            hea: [1.6189, 1.3830, 1.1919, 1.0458, 0.9220, 0.8205, 0.7305, 0.6502, 0.5950, 0.5545, 0.5333, 0.5189, 0.5181, 0.5176, 0.5172, 0.5119],
            heb: [0.4770, 0.5747, 0.6527, 0.7223, 0.7582, 0.7957, 0.8279, 0.8553, 0.8757, 0.8903, 0.8997, 0.9073, 0.9122, 0.9171, 0.9217, 0.9267]
        };
    }
}

// ===================== ceilingGF  =====================
function ceilingGF(pnArr, peArr, GF) {
    const { n2a, n2b, hea, heb } = getCoefficients();
    let cmax = 0;
    for (let i = 0; i < 16; i++) {
        const PN2 = pnArr[i],
            PHe = peArr[i],
            Pt = PN2 + PHe;
        if (Pt <= 0) continue;
        const A = ((n2a[i] * PN2) + (hea[i] * PHe)) / Pt;
        const B = ((n2b[i] * PN2) + (heb[i] * PHe)) / Pt;
        const denom = GF - (GF * B) + B; // B + GF*(1-B)
        const Pmin = (Pt - A * GF) * (B / Math.max(denom, 1e-9));
        if (Pmin > cmax) cmax = Pmin;
    }
    return cmax;
}

// ===================== SATURAZIONE: DISCESA + FONDO ===============================
function runTissuesWithDescent() {
    const { halftimen2, halftimehe } = getCoefficients();
    const { depth_m, bottomMin, descRate } = getDiveParams();
    const gases = getGases();
    const PH2O = 0.0627;

    // iniziale (aria a 1 bar)
    const PN2_0 = 0.7902 * (1.0 - PH2O);
    let pn = Array(16).fill(PN2_0);
    let pe = Array(16).fill(0);

    const kN2 = halftimen2.map(ht => Math.log(2) / (ht * 60));
    const kHe = halftimehe.map(ht => Math.log(2) / (ht * 60));

    // DISCESA su gas di fondo
    integrateTravelTissues(pn, pe, kN2, kHe, gases[0], 0, depth_m, descRate, PH2O);

    // FONDO su gas di fondo
    const Pamb = 1 + depth_m / 10;
    const PiN2 = gases[0].FN2 * (Pamb - PH2O);
    const PiHe = gases[0].FHe * (Pamb - PH2O);
    const totalSec = Math.round(bottomMin * 60);
    for (let t = 0; t < totalSec; t += STEP_SEC) {
        for (let i = 0; i < 16; i++) {
            pn[i] += (PiN2 - pn[i]) * (1 - Math.exp(-kN2[i] * STEP_SEC));
            pe[i] += (PiHe - pe[i]) * (1 - Math.exp(-kHe[i] * STEP_SEC));
        }
    }

    // (debug )
    let lines = [];
    lines.push(`\n\n Nerd things:\nTissue saturation after descent + ${bottomMin} min @ ${depth_m} m\n`);
    lines.push("Idx | PN₂ (bar) | PHe (bar) | Ptot (bar)");
    for (let i = 0; i < 16; i++) {
        lines.push(`${pad2(i+1)} | ${r3(pn[i])} | ${r3(pe[i])} | ${r3(pn[i]+pe[i])}`);
    }
    $w('#text27').text = lines.join("\n");

    return { pn, pe };
}

// integrazione tessuti durante spostamento verticale a gas fisso
function integrateTravelTissues(pn, pe, kN2, kHe, gas, fromDepth, toDepth, rate_m_per_min, PH2O) {
    if (!isFinite(fromDepth) || !isFinite(toDepth) || rate_m_per_min <= 0) return;
    const delta = toDepth - fromDepth;
    const dist = Math.abs(delta);
    if (dist < 1e-6) return;
    const steps = Math.max(1, Math.ceil(dist));
    const stepM = delta / steps;
    const dtMin = Math.abs(stepM) / rate_m_per_min;
    const dtSec = dtMin * 60;

    for (let iStep = 0; iStep < steps; iStep++) {
        const midDepth = fromDepth + (iStep + 0.5) * stepM;
        const Pamb = 1 + Math.max(0, midDepth) / 10;
        const PiN2 = gas.FN2 * (Pamb - PH2O);
        const PiHe = gas.FHe * (Pamb - PH2O);
        for (let i = 0; i < 16; i++) {
            pn[i] += (PiN2 - pn[i]) * (1 - Math.exp(-kN2[i] * dtSec));
            pe[i] += (PiHe - pe[i]) * (1 - Math.exp(-kHe[i] * dtSec));
        }
    }
}

// =============== STEP 2 — Ceiling iniziale + prima tappa ===========================
function showCeilingInfo(pn, pe) {
    const depth_m = n('#depth');
    const pressione = 1 + depth_m / 10;
    const gflow = n('#gfLow') / 100;
    const gfhi = n('#gfHigh') / 100;

    // GF info
    let GFm = (gfhi - gflow) / ((pressione - 1) * 10);
    let GF = gfhi - GFm * ((pressione - 1) * 10);
    let gffinal = Math.min(Math.max(GF, gflow), gfhi);

    // Prima tappa (semper arrotondata a SALIRE al multiplo di 3 m)
    const ceiling0_raw = ceilingGF(pn, pe, gflow);
    const ceiling0 = ceiling0_raw + FIRST_STOP_EPS;
    let primatappamax = Math.ceil(((ceiling0 - 1) * 10) / 3) * 3;
    if (primatappamax < 3) primatappamax = 3;

    let lines = [];
    lines.push(`Model: ZHL-16${currentModel()} + GF ${Math.round(gflow*100)}/${Math.round(gfhi*100)}`);
    lines.push(`GF (at current Pamb): ${gffinal.toFixed(2)}`);
    lines.push(`Ceiling: ${(((ceiling0_raw-1)*10)).toFixed(1)} m`);
    lines.push(`First stop depth: ${primatappamax} m`);
    $w('#text29').text = lines.join("\n");
}

// =============== PIANO DECO + RISALITA ALLA PRIMA TAPPA ===========================
function runDecoPlan(pn, pe) {
    const gflow = n('#gfLow') / 100,
        gfhi = n('#gfHigh') / 100;
    const gases = getGases();
    const { halftimen2, halftimehe } = getCoefficients();
    const PH2O = 0.0627;
    const { depth_m, ascRate } = getDiveParams();

    const kN2 = halftimen2.map(ht => Math.log(2) / (ht * 60));
    const kHe = halftimehe.map(ht => Math.log(2) / (ht * 60));

    function pickBestGas(depthM) {
        const Pamb = 1 + depthM / 10;
        let usable = gases.filter(g => isFinite(g.switchDepth) && depthM <= g.switchDepth);
        usable = usable.filter(g => g.FO2 * Pamb <= g.ppo2lim + 1e-6);
        if (!usable.length) return gases[0];
        usable.sort((a, b) => b.FO2 - a.FO2);
        return usable[0];
    }

    // copie tessuti
    let decopn = pn.slice(),
        decope = pe.slice();

    // prima tappa da ceiling con GF_low
    const ceiling0_raw = ceilingGF(decopn, decope, gflow);
    const ceiling0 = ceiling0_raw + FIRST_STOP_EPS;
    let primatappamax = Math.ceil(((ceiling0 - 1) * 10) / 3) * 3;
    if (primatappamax < 3) primatappamax = 3;

    // integra RISALITA fondo -> prima tappa con gas dinamico (coerente col planner)
    {
        const from = depth_m,
            to = primatappamax;
        if (ascRate > 0 && from > to) {
            const delta = from - to;
            const steps = Math.max(1, Math.ceil(delta));
            for (let i = 0; i < steps; i++) {
                const d1 = from - i;
                const d2 = from - (i + 1);
                const mid = (d1 + d2) / 2;
                const gas = pickBestGas(Math.max(0, mid));
                integrateTravelTissues(decopn, decope, kN2, kHe, gas, d1, d2, ascRate, PH2O);
            }
        }
    }

    // retta GF
    const GFmdeco = (gfhi - gflow) / primatappamax;

    let counterstep = primatappamax;
    let stops = [];

    while (counterstep > 0) {
        let GF = gfhi - GFmdeco * counterstep;
        if (GF < gflow) GF = gflow;
        if (GF > gfhi) GF = gfhi;

        const gasNow = pickBestGas(counterstep);
        const PambStop = 1 + counterstep / 10;
        const PiN2 = gasNow.FN2 * (PambStop - PH2O);
        const PiHe = gasNow.FHe * (PambStop - PH2O);

        let holdSec = 0;
        let decoceiling = ceilingGF(decopn, decope, GF);
        const nextPamb = PambStop - 0.3;
        const eps = (counterstep <= SHALLOW_THRESHOLD) ? CEIL_EPS_SHALLOW : CEIL_EPS_DEEP;

        while (decoceiling > nextPamb + eps) {
            for (let i = 0; i < 16; i++) {
                decopn[i] += (PiN2 - decopn[i]) * (1 - Math.exp(-kN2[i] * STEP_SEC));
                decope[i] += (PiHe - decope[i]) * (1 - Math.exp(-kHe[i] * STEP_SEC));
            }
            holdSec += STEP_SEC;
            decoceiling = ceilingGF(decopn, decope, GF);
        }

        const holdMin = (ROUNDING === "floor") ? Math.floor(holdSec / 60) : Math.round(holdSec / 60);
        if (holdMin > 0) {
            stops.push({ depth: counterstep, time: holdMin, GF, ceiling: decoceiling, gas: gasNow });
        }
        counterstep -= 3;
    }

    // ---- Consumi ----
    const usage = computeGasUsage(stops, gases);

    // ---- Runtime cumulativo (min) ----
    const { depth_m: D, bottomMin: BT, descRate, ascRate: AR } = getDiveParams();
    let runtimeMin = 0;
    if (isFinite(D) && descRate > 0) runtimeMin += D / descRate; // discesa
    if (isFinite(BT) && BT > 0) runtimeMin += BT; // fondo
    let rtLeaveBottom = runtimeMin; // runtime quando si lascia il fondo
    if (stops.length > 0 && AR > 0) runtimeMin += (D - stops[0].depth) / AR; // alla 1ª tappa
    const firstStopRt = runtimeMin;

    for (let i = 0; i < stops.length; i++) {
        const s = stops[i];
        runtimeMin += s.time;
        s.runtime = runtimeMin;
        if (i < stops.length - 1 && AR > 0) {
            const nextDepth = stops[i + 1].depth;
            runtimeMin += (s.depth - nextDepth) / AR;
        }
    }

    // ---- END & Gas Density (solo gas di fondo) ----
    const infoBottom = bottomGasInfo(gases[0], D);

    // ---- CNS% totale (NOAA) su discesa, fondo, risalite, soste) ----
    const cnsTotal = computeCNSPercent(stops, gases);

    // ===== Output piano (allineato, depth/time evidenziati) =====
    const DEP_W = 5,
        TIME_W = 6,
        RT_W = 6,
        GAS_W = 18,
        PPO2_W = 5;

    let rows = [];
    rows.push(spanBase(`PLAN — Single OC (ZHL-16${currentModel()} + GF ${Math.round(gflow*100)}/${Math.round(gfhi*100)})`, COLOR_BASE_TEXT));
    rows.push(spanDim(`(ppO₂ shown at stop depth)\n`, COLOR_DIM_TEXT));
    rows.push(""); // riga vuota

    // RIEPILOGO GAS DI FONDO: END & Densità
    rows.push(spanBase(`Bottom gas: ${gasDisplay(gases[0]).label}`, COLOR_BASE_TEXT));
    rows.push(spanDim(`\nEND @ ${D} m: ${infoBottom.ENDm.toFixed(0)} m | Gas density @ ${D} m: ${infoBottom.density_gL.toFixed(2)} g/L\n\n\n`, COLOR_DIM_TEXT));
    rows.push(""); // riga vuota

    // Riga "leave bottom" + runtime fino alla 1ª tappa
    if (stops.length) {
        rows.push(
            spanDim(`Leave bottom (${Math.round(rtLeaveBottom)})`, COLOR_DIM_TEXT) +
            spanBase(`\n → ascend to first stop @ `, COLOR_BASE_TEXT) +
            spanHilite(rcol(`${stops[0].depth} m`, DEP_W)) +
            spanBase(`    `, COLOR_BASE_TEXT) +
            spanDim(`(${Math.round(firstStopRt)})`, COLOR_DIM_TEXT)
        );
    }

    // Soste
    for (const s of stops) {
        const depthStr = `${s.depth} m`;
        const timeStr = `${s.time} min`;
        const PambStop = 1 + s.depth / 10;
        const ppO2 = (s.gas.FO2 * PambStop).toFixed(2);
        const runStr = `(${Math.round(s.runtime)})`;
        const gdisp = gasDisplay(s.gas);
        const gasStr = gdisp.label;

        const line =
            spanBase("\nStop @ ", COLOR_BASE_TEXT) +
            spanHilite(rcol(depthStr, DEP_W)) + spanBase("  ", COLOR_BASE_TEXT) +
            spanHilite(rcol(timeStr, TIME_W)) + spanBase("  ", COLOR_BASE_TEXT) +
            spanDim(rcol(runStr, RT_W), COLOR_DIM_TEXT) + spanBase("  ", COLOR_BASE_TEXT) +
            spanBase("--> ", COLOR_BASE_TEXT) +
            spanDim(lcol(gasStr, GAS_W), COLOR_DIM_TEXT) + spanBase("  ", COLOR_BASE_TEXT) +
            spanDim(`ppO₂ ${rcol(ppO2, PPO2_W)}`, COLOR_DIM_TEXT);

        rows.push(line);
    }

    // Consumi
    rows.push('\n' + spanBase('\nGas usage (surface liters):\n', COLOR_BASE_TEXT));
    let totalNL = 0;
    for (const it of usage) {
        totalNL += it.liters;
        const lbl = lcol(it.label, 18);
        const val = rcol(Math.round(it.liters).toString(), 8);
        rows.push(spanDim(`• ${lbl}  ${val} NL\n`, COLOR_DIM_TEXT));
    }
    rows.push(spanDim(`Total${' '.repeat(17)}${rcol(Math.round(totalNL).toString(), 8)} NL\n`, COLOR_DIM_TEXT));

    // CNS
    rows.push('');
    rows.push(spanBase(`\nCNS total: ${cnsTotal.toFixed(0)}%\n\n\n\n\n`, COLOR_BASE_TEXT));

    const html =
        `<pre style="
      margin:0; white-space:pre-wrap;
      font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, 'Courier New', monospace;
      font-size:14px; line-height:1.4; color:${COLOR_BASE_TEXT};
    ">` + rows.join("") + `</pre>`;

    if ($w('#planText').html !== undefined) $w('#planText').html = html;
    else if ($w('#planText').value !== undefined) $w('#planText').value = html;
    else $w('#planText').text = rows.map(stripTags).join("\n");

    // --- Snapshot tessuti immediatamente a superficie (Air 21/79) ---
    function renderSurfaceTissues(decopn, decope, lastStopDepth, ascRate, kN2, kHe, PH2O) {
        let pnS = decopn.slice();
        let peS = decope.slice();

        // Risalita ultima sosta -> superficie con aria (21/79)
        if (isFinite(lastStopDepth) && lastStopDepth > 0 && ascRate > 0) {
            const air = { FO2: 0.21, FHe: 0.00, FN2: 0.79 };
            integrateTravelTissues(pnS, peS, kN2, kHe, air, lastStopDepth, 0, ascRate, PH2O);
        }

        // Snapshot NOW @ surface
        let lines = [];
        lines.push("\n\n\nTissue saturation @ surface (Air 21/79)\n");
        lines.push("Idx | PN₂ (bar) | PHe (bar) | Ptot (bar)");
        for (let i = 0; i < 16; i++) {
            const PN2 = pnS[i];
            const PHe = peS[i];
            const Ptot = PN2 + PHe;
            lines.push(`${pad2(i+1)} | ${r3(PN2)} | ${r3(PHe)} | ${r3(Ptot)}`);
        }

        if ($w('#text37').text !== undefined) {
            $w('#text37').text = lines.join("\n");
        }
    }
    // --- Snapshot tessuti a superficie ---
    const lastStopDepth = (stops.length ? stops[stops.length - 1].depth : 0);
    renderSurfaceTissues(decopn, decope, lastStopDepth, AR, kN2, kHe, PH2O);

    return stops;
}

// ================= GAS (robusto a campi vuoti / EAN/O2) ============================
function getGases() {
    function _raw(id) { return String($w(id).value || '').trim(); }

    function _num(id) { const s = _raw(id).replace(',', '.'); const v = Number(s); return isFinite(v) ? v : NaN; }

    function _pct(id, def = 0) { const v = _num(id); return isFinite(v) ? v / 100 : def; }

    // usa #maxppo2 per TUTTE le miscele
    const maxppo2 = _num('#maxppo2');

    let gases = [
        { name: "Bottom", FO2: _pct('#o20', 0), FHe: _pct('#he0', 0), ppo2lim: maxppo2 },
        { name: "Deco1", FO2: _pct('#o21', 0), FHe: _pct('#he1', 0), ppo2lim: maxppo2 },
        { name: "Deco2", FO2: _pct('#o22', 0), FHe: _pct('#he2', 0), ppo2lim: maxppo2 },
        { name: "Deco3", FO2: _pct('#o23', 0), FHe: _pct('#he3', 0), ppo2lim: maxppo2 },
        { name: "Deco4", FO2: _pct('#o24', 0), FHe: _pct('#he4', 0), ppo2lim: maxppo2 }
    ];

    gases.forEach(g => {
        g.FO2 = Math.min(1, Math.max(0, isFinite(g.FO2) ? g.FO2 : 0));
        g.FHe = Math.min(1, Math.max(0, isFinite(g.FHe) ? g.FHe : 0));
        let sum = g.FO2 + g.FHe;
        if (sum > 1) {
            g.FO2 = g.FO2 / sum;
            g.FHe = g.FHe / sum;
        }
        g.FN2 = 1 - g.FO2 - g.FHe;

        if (g.FO2 > 0 && isFinite(g.ppo2lim) && g.ppo2lim > 0) {
            const PambMax = g.ppo2lim / g.FO2;
            g.switchDepth = (PambMax - 1) * 10;
        } else {
            g.switchDepth = NaN;
        }
    });
    return gases.filter(g => isFinite(g.FN2));
}

// ===================== GAS USAGE (surface liters) =================================
function getDiveParams() {
    const depth_m = n('#depth');
    const bottomMin = n('#bottomTime');
    let descRate = n('#descRate');
    let ascRate = n('#ascRate');
    const rmv = n('#rmv');
    if (!isFinite(descRate) || descRate <= 0) descRate = 20;
    if (!isFinite(ascRate) || ascRate <= 0) ascRate = 10;
    return { depth_m, bottomMin, descRate, ascRate, rmv };
}

function gasAtDepth(gases, depthM) {
    const Pamb = 1 + depthM / 10;
    let usable = gases.filter(g => isFinite(g.switchDepth) && depthM <= g.switchDepth);
    usable = usable.filter(g => g.FO2 * Pamb <= g.ppo2lim + 1e-6);
    if (!usable.length) return gases[0];
    usable.sort((a, b) => b.FO2 - a.FO2);
    return usable[0];
}

function integrateTravel(gases, fromDepth, toDepth, rate_m_per_min, rmv, accum) {
    if (!isFinite(fromDepth) || !isFinite(toDepth) || rate_m_per_min <= 0) return;
    const delta = toDepth - fromDepth,
        dist = Math.abs(delta);
    if (dist < 1e-6) return;
    const steps = Math.max(1, Math.ceil(dist));
    const stepM = delta / steps;
    const dtMin = Math.abs(stepM) / rate_m_per_min;

    for (let i = 0; i < steps; i++) {
        const midDepth = fromDepth + (i + 0.5) * stepM;
        const Pamb = 1 + Math.max(0, midDepth) / 10;
        const gas = gasAtDepth(gases, Math.max(0, midDepth));
        const key = gasKey(gas);
        const consSL = rmv * Pamb * dtMin;
        accum[key] = (accum[key] || 0) + consSL;
    }
}

function integrateHold(gases, depthM, minutes, rmv, accum) {
    if (minutes <= 0) return;
    const Pamb = 1 + depthM / 10;
    const gas = gasAtDepth(gases, depthM);
    const key = gasKey(gas);
    const cons = rmv * Pamb * minutes;
    accum[key] = (accum[key] || 0) + cons;
}

// --- integrazione consumi con GAS FORZATO (discesa e fondo) ---
function integrateTravelWithGas(gas, fromDepth, toDepth, rate_m_per_min, rmv, accum) {
    if (!isFinite(fromDepth) || !isFinite(toDepth) || rate_m_per_min <= 0) return;
    const delta = toDepth - fromDepth,
        dist = Math.abs(delta);
    if (dist < 1e-6) return;
    const steps = Math.max(1, Math.ceil(dist));
    const stepM = delta / steps;
    const dtMin = Math.abs(stepM) / rate_m_per_min;

    const key = gasKey(gas);
    for (let i = 0; i < steps; i++) {
        const midDepth = fromDepth + (i + 0.5) * stepM;
        const Pamb = 1 + Math.max(0, midDepth) / 10;
        const consSL = rmv * Pamb * dtMin;
        accum[key] = (accum[key] || 0) + consSL;
    }
}

function integrateHoldWithGas(gas, depthM, minutes, rmv, accum) {
    if (minutes <= 0) return;
    const Pamb = 1 + depthM / 10;
    const key = gasKey(gas);
    const cons = rmv * Pamb * minutes;
    accum[key] = (accum[key] || 0) + cons;
}

function gasKey(g) { return `${g.name}|${Math.round(g.FO2*100)}/${Math.round(g.FHe*100)}`; }

function gasLabelFromKey(k) {
    const [_, mix] = k.split('|');
    const [o2s, hes] = mix.split('/').map(Number);
    if (o2s === 21 && hes === 0) return 'Air';
    if (o2s === 100 && hes === 0) return 'Oxygen';
    if (hes > 0) return `Trimix ${o2s}/${hes}`;
    if (o2s > 21) return `Nitrox ${o2s}`;
    return `Gas ${mix}`;
}

function computeGasUsage(stops, gases) {
    const { depth_m, bottomMin, descRate, ascRate, rmv } = getDiveParams();
    const accum = {};
    const bottomGas = gases[0]; // forza la miscela di fondo

    // PRIMA: discesa su bottom gas
    integrateTravelWithGas(bottomGas, 0, depth_m, descRate, rmv, accum);

    // POI: fondo su bottom gas
    integrateHoldWithGas(bottomGas, depth_m, bottomMin, rmv, accum);

    // Risalita fino alla prima tappa: dinamico (switch appena è lecito)
    const firstStopDepth = (stops.length ? stops[0].depth : 3);
    integrateTravel(gases, depth_m, firstStopDepth, ascRate, rmv, accum);

    // Soste + risalite tra tappe: dinamico
    for (let i = 0; i < stops.length; i++) {
        const s = stops[i];
        integrateHold(gases, s.depth, s.time, rmv, accum);
        const nextDepth = (i < stops.length - 1) ? stops[i + 1].depth : 0;
        integrateTravel(gases, s.depth, nextDepth, ascRate, rmv, accum);
    }

    const items = Object.entries(accum).map(([k, liters]) => ({ key: k, label: gasLabelFromKey(k), liters }));
    items.sort((a, b) => a.label.localeCompare(b.label));
    return items;
}

// ===================== END & GAS DENSITY (gas di fondo) ===========================
// END (m) assumendo solo N2 come narcotico (O2 non narcotico): END = ((FN2/0.79)*(D+10))-10
function computeENDmeters(bottomGas, depth_m) {
    const FN2 = bottomGas.FN2;
    const Pamb = 1 + depth_m / 10;
    const END_ambient = (FN2 / 0.79) * Pamb; // equivalente air pressure
    return Math.max(0, (END_ambient - 1) * 10);
}

// densità mix @ 1 bar (kg/m^3) a ~20°C: He 0.1786, N2 1.2506, O2 1.331
function gasDensityAtDepth(bottomGas, depth_m) {
    const rhoHe = 0.1786,
        rhoN2 = 1.2506,
        rhoO2 = 1.3310;
    const rho1bar = bottomGas.FHe * rhoHe + bottomGas.FN2 * rhoN2 + bottomGas.FO2 * rhoO2; // kg/m3
    const Pamb = 1 + depth_m / 10;
    const rhoDepth = rho1bar * Pamb; // kg/m3
    return rhoDepth * 1.0; // kg/m3 -> kg/m3 (convertiamo dopo in g/L)
}

function bottomGasInfo(bottomGas, depth_m) {
    const ENDm = computeENDmeters(bottomGas, depth_m);
    const rho_kgm3 = gasDensityAtDepth(bottomGas, depth_m);
    const density_gL = rho_kgm3; // 1 kg/m3 = 1 g/L
    return { ENDm, density_gL };
}

// ===================== CNS NOAA ===================================================
// Tabella NOAA (minuti per 100% CNS) a vari ppO2 (bar). Linear interp. Sotto 0.5 bar = 0.
const NOAA_TABLE = [
    { pp: 1.6, min: 45 }, { pp: 1.5, min: 120 }, { pp: 1.4, min: 150 }, { pp: 1.3, min: 180 },
    { pp: 1.2, min: 210 }, { pp: 1.1, min: 240 }, { pp: 1.0, min: 300 }, { pp: 0.9, min: 360 },
    { pp: 0.8, min: 450 }, { pp: 0.7, min: 570 }, { pp: 0.6, min: 720 }, { pp: 0.5, min: 1440 }
];

function minutesFor100CNS(pp) {
    if (pp < 0.5) return Infinity;
    // clamp in range
    if (pp >= NOAA_TABLE[0].pp) return NOAA_TABLE[0].min;
    if (pp <= NOAA_TABLE[NOAA_TABLE.length - 1].pp) return NOAA_TABLE[NOAA_TABLE.length - 1].min;
    // linear interp between surrounding nodes
    for (let i = 0; i < NOAA_TABLE.length - 1; i++) {
        const a = NOAA_TABLE[i],
            b = NOAA_TABLE[i + 1];
        if (pp <= a.pp && pp >= b.pp) {
            const t = (pp - b.pp) / (a.pp - b.pp);
            return b.min + t * (a.min - b.min);
        }
    }
    return Infinity;
}

function cnsIncrement(pp, minutes) {
    const M = minutesFor100CNS(pp);
    if (!isFinite(M) || M === Infinity) return 0;
    return (minutes / M) * 100;
}
// calcolo CNS% integrando a step di 1 m durante discese/risalite + soste + fondo
function computeCNSPercent(stops, gases) {
    const { depth_m, bottomMin, descRate, ascRate } = getDiveParams();
    let cns = 0;

    // helper: CNS su travel (1 m per step)
    function cnsTravel(fromDepth, toDepth, rate_m_per_min) {
        if (!isFinite(fromDepth) || !isFinite(toDepth) || rate_m_per_min <= 0) return;
        const delta = toDepth - fromDepth,
            dist = Math.abs(delta);
        if (dist < 1e-6) return;
        const steps = Math.max(1, Math.ceil(dist));
        const stepM = delta / steps;
        const dtMin = Math.abs(stepM) / rate_m_per_min;
        for (let i = 0; i < steps; i++) {
            const midDepth = fromDepth + (i + 0.5) * stepM;
            const gas = gasAtDepth(gases, Math.max(0, midDepth));
            const ppO2 = gas.FO2 * (1 + Math.max(0, midDepth) / 10);
            cns += cnsIncrement(ppO2, dtMin);
        }
    }
    // helper: CNS su hold
    function cnsHold(depthM, minutes) {
        if (minutes <= 0) return;
        const gas = gasAtDepth(gases, depthM);
        const ppO2 = gas.FO2 * (1 + depthM / 10);
        cns += cnsIncrement(ppO2, minutes);
    }

    // 1) discesa 0->fondo (gas fondo)
    cnsTravel(0, depth_m, descRate);
    // 2) fondo
    cnsHold(depth_m, bottomMin);
    // 3) risalita al primo stop
    const firstStopDepth = (stops.length ? stops[0].depth : 3);
    cnsTravel(depth_m, firstStopDepth, ascRate);
    // 4) soste + risalite tra tappe
    for (let i = 0; i < stops.length; i++) {
        const s = stops[i];
        cnsHold(s.depth, s.time);
        const nextDepth = (i < stops.length - 1) ? stops[i + 1].depth : 0;
        cnsTravel(s.depth, nextDepth, ascRate);
    }

    return Math.max(0, cns);
}

// ============================ HELPERS =============================================
function n(id) { return Number(String($w(id).value || '').replace(',', '.')); }

function pct(id) { const v = n(id); return isFinite(v) ? v / 100 : NaN; }

function pad2(x) { return String(x).padStart(2, '0'); }

function r3(x) { return (Math.round(x * 1000) / 1000).toFixed(3); }

function rcol(s, w) { s = String(s); return (' '.repeat(w) + s).slice(-w); }

function lcol(s, w) { s = String(s); return (s + ' '.repeat(w)).slice(0, w); }

function spanBase(txt, color) { return `<span style="color:${color};">${escapeHtml(txt)}</span>`; }

function spanDim(txt, color) { return `<span style="color:${color};">${escapeHtml(txt)}</span>`; }

function spanHilite(txt) {
    return `<span style="color:${HILITE_FG}; background-color:${HILITE_BG}; padding:0 2px; border-radius:2px;">${escapeHtml(txt)}</span>`;
}

function escapeHtml(s) { return String(s).replace(/[&<>"']/g, m => ({ '&': '&amp;', '<': '&lt;', '>': '&gt;', '"': '&quot;', "'": '&#039;' } [m])); }

function stripTags(s) { return String(s).replace(/<[^>]+>/g, ''); }

function gasDisplay(g) {
    const o2 = Math.round(g.FO2 * 100),
        he = Math.round(g.FHe * 100);
    let type, label;
    if (o2 === 21 && he === 0) {
        type = 'air';
        label = 'Air';
    } else if (o2 === 100 && he === 0) {
        type = 'oxygen';
        label = 'Oxygen';
    } else if (he > 0) {
        type = 'trimix';
        label = `Trimix ${o2}/${he}`;
    } else if (o2 > 21 && he === 0) {
        type = 'nitrox';
        label = `Nitrox ${o2}`;
    } else {
        type = 'air';
        label = `Gas ${o2}/${he}`;
    }
    return { type, label, o2, he };
}

// --- Snapshot tessuti immediatamente a superficie (Air 21/79) ---
function renderSurfaceTissues(decopn, decope, lastStopDepth, ascRate, kN2, kHe, PH2O) {
    let pnS = decopn.slice();
    let peS = decope.slice();

    // Risalita ultima sosta -> superficie con aria (21/79)
    if (isFinite(lastStopDepth) && lastStopDepth > 0 && ascRate > 0) {
        const air = { FO2: 0.21, FHe: 0.00, FN2: 0.79 };
        integrateTravelTissues(pnS, peS, kN2, kHe, air, lastStopDepth, 0, ascRate, PH2O);
    }

    // Snapshot NOW @ surface
    let lines = [];
    lines.push("Tissue saturation @ surface (Air 21/79)");
    lines.push("Idx | PN₂ (bar) | PHe (bar) | Ptot (bar)");
    for (let i = 0; i < 16; i++) {
        const PN2 = pnS[i];
        const PHe = peS[i];
        const Ptot = PN2 + PHe;
        lines.push(`${pad2(i+1)} | ${r3(PN2)} | ${r3(PHe)} | ${r3(Ptot)}`);
    }

    if ($w('#text37').text !== undefined) {
        $w('#text37').text = lines.join("\n");
    }
}// ================== PLANNER ZHL-16B/C + GF (dt=1s, PH2O=0.0627) ==================
$w.onReady(() => {
    $w('#planBtn').onClick(() => {
        const { pn, pe } = runTissuesWithDescent(); // Step 1: discesa + fondo
        showCeilingInfo(pn, pe); //     : ceiling iniziale + prima tappa
        runDecoPlan(pn, pe); // Step 3: risalita a prima tappa + piano deco + consumi + END/Density + CNS
    });
});

// === Lettura modello B/C dal RadioGroup ===
function currentModel() {
    try {
        const el = $w('#radioGroup1');
        if (el && typeof el.value === 'string') {
            const v = el.value.trim().toUpperCase();
            return (v === 'C') ? 'C' : 'B';
        }
    } catch (e) {}
    return 'B';
}

// --- Parametri numerici / fine tuning  (arrotondamenti così sono più restrittivo in profondità e più perimissivo in superficie) ---
const STEP_SEC = 1;
const SHALLOW_THRESHOLD = 15;
const CEIL_EPS_DEEP = -0.012;
const CEIL_EPS_SHALLOW = +0.001;
const ROUNDING = "floor";
const FIRST_STOP_EPS = 0.03;

// --- Stile output ---
const USE_HTML_COLORS = true;
const COLOR_BASE_TEXT = "#ffffff";
const COLOR_DIM_TEXT = "#9aa0a6";
const HILITE_BG = "#64ffda";
const HILITE_FG = "#00332b";

// ==================== Coefficienti ZHL-16B / ZHL-16C ==============================
function getCoefficients() {
    const model = currentModel();
    if (model === "B") {
        return {
            halftimen2: [4.0, 8.0, 12.5, 18.5, 27.0, 38.3, 54.3, 77.0, 109.0, 146.0, 187.0, 239.0, 305.0, 390.0, 498.0, 635.0],
            halftimehe: [1.5, 3.0, 4.7, 7.0, 10.2, 14.5, 20.5, 29.1, 41.1, 55.1, 70.6, 90.2, 115.1, 147.2, 187.9, 239.6],
            n2a: [1.2599, 1.0, 0.8618, 0.7562, 0.6667, 0.5933, 0.5282, 0.4701, 0.4187, 0.3798, 0.3497, 0.3223, 0.2971, 0.2737, 0.2523, 0.2327],
            n2b: [0.505, 0.6514, 0.7222, 0.7725, 0.8125, 0.8434, 0.8693, 0.891, 0.9092, 0.9222, 0.9319, 0.9403, 0.9477, 0.9544, 0.9602, 0.9653],
            hea: [1.7435, 1.3838, 1.1925, 1.0465, 0.9226, 0.8211, 0.7309, 0.6506, 0.5794, 0.5256, 0.484, 0.446, 0.4112, 0.3788, 0.3492, 0.322],
            heb: [0.1911, 0.4295, 0.5446, 0.6265, 0.6917, 0.742, 0.7841, 0.8195, 0.8491, 0.8703, 0.886, 0.8997, 0.9118, 0.9226, 0.9321, 0.9404]
        };
    } else {
        return {
            halftimen2: [4.0, 8.0, 12.5, 18.5, 27.0, 38.3, 54.3, 77.0, 109.0, 146.0, 187.0, 239.0, 305.0, 390.0, 498.0, 635.0],
            halftimehe: [1.51, 3.02, 4.72, 6.99, 10.21, 14.48, 20.53, 29.11, 41.20, 55.19, 70.69, 90.34, 115.29, 147.42, 188.24, 240.03],
            n2a: [1.1696, 1.0, 0.8618, 0.7562, 0.6667, 0.5933, 0.5282, 0.4701, 0.4187, 0.3798, 0.3497, 0.3223, 0.2971, 0.2737, 0.2523, 0.2327],
            n2b: [0.5578, 0.6514, 0.7222, 0.7825, 0.8126, 0.8434, 0.8693, 0.8910, 0.9092, 0.9222, 0.9319, 0.9403, 0.9477, 0.9544, 0.9602, 0.9653],
            hea: [1.6189, 1.3830, 1.1919, 1.0458, 0.9220, 0.8205, 0.7305, 0.6502, 0.5950, 0.5545, 0.5333, 0.5189, 0.5181, 0.5176, 0.5172, 0.5119],
            heb: [0.4770, 0.5747, 0.6527, 0.7223, 0.7582, 0.7957, 0.8279, 0.8553, 0.8757, 0.8903, 0.8997, 0.9073, 0.9122, 0.9171, 0.9217, 0.9267]
        };
    }
}

// ===================== ceilingGF  =====================
function ceilingGF(pnArr, peArr, GF) {
    const { n2a, n2b, hea, heb } = getCoefficients();
    let cmax = 0;
    for (let i = 0; i < 16; i++) {
        const PN2 = pnArr[i],
            PHe = peArr[i],
            Pt = PN2 + PHe;
        if (Pt <= 0) continue;
        const A = ((n2a[i] * PN2) + (hea[i] * PHe)) / Pt;
        const B = ((n2b[i] * PN2) + (heb[i] * PHe)) / Pt;
        const denom = GF - (GF * B) + B; // B + GF*(1-B)
        const Pmin = (Pt - A * GF) * (B / Math.max(denom, 1e-9));
        if (Pmin > cmax) cmax = Pmin;
    }
    return cmax;
}

// ===================== SATURAZIONE: DISCESA + FONDO ===============================
function runTissuesWithDescent() {
    const { halftimen2, halftimehe } = getCoefficients();
    const { depth_m, bottomMin, descRate } = getDiveParams();
    const gases = getGases();
    const PH2O = 0.0627;

    // iniziale (aria a 1 bar)
    const PN2_0 = 0.7902 * (1.0 - PH2O);
    let pn = Array(16).fill(PN2_0);
    let pe = Array(16).fill(0);

    const kN2 = halftimen2.map(ht => Math.log(2) / (ht * 60));
    const kHe = halftimehe.map(ht => Math.log(2) / (ht * 60));

    // DISCESA su gas di fondo
    integrateTravelTissues(pn, pe, kN2, kHe, gases[0], 0, depth_m, descRate, PH2O);

    // FONDO su gas di fondo
    const Pamb = 1 + depth_m / 10;
    const PiN2 = gases[0].FN2 * (Pamb - PH2O);
    const PiHe = gases[0].FHe * (Pamb - PH2O);
    const totalSec = Math.round(bottomMin * 60);
    for (let t = 0; t < totalSec; t += STEP_SEC) {
        for (let i = 0; i < 16; i++) {
            pn[i] += (PiN2 - pn[i]) * (1 - Math.exp(-kN2[i] * STEP_SEC));
            pe[i] += (PiHe - pe[i]) * (1 - Math.exp(-kHe[i] * STEP_SEC));
        }
    }

    // (debug )
    let lines = [];
    lines.push(`\n\n Nerd things:\nTissue saturation after descent + ${bottomMin} min @ ${depth_m} m\n`);
    lines.push("Idx | PN₂ (bar) | PHe (bar) | Ptot (bar)");
    for (let i = 0; i < 16; i++) {
        lines.push(`${pad2(i+1)} | ${r3(pn[i])} | ${r3(pe[i])} | ${r3(pn[i]+pe[i])}`);
    }
    $w('#text27').text = lines.join("\n");

    return { pn, pe };
}

// integrazione tessuti durante spostamento verticale a gas fisso
function integrateTravelTissues(pn, pe, kN2, kHe, gas, fromDepth, toDepth, rate_m_per_min, PH2O) {
    if (!isFinite(fromDepth) || !isFinite(toDepth) || rate_m_per_min <= 0) return;
    const delta = toDepth - fromDepth;
    const dist = Math.abs(delta);
    if (dist < 1e-6) return;
    const steps = Math.max(1, Math.ceil(dist));
    const stepM = delta / steps;
    const dtMin = Math.abs(stepM) / rate_m_per_min;
    const dtSec = dtMin * 60;

    for (let iStep = 0; iStep < steps; iStep++) {
        const midDepth = fromDepth + (iStep + 0.5) * stepM;
        const Pamb = 1 + Math.max(0, midDepth) / 10;
        const PiN2 = gas.FN2 * (Pamb - PH2O);
        const PiHe = gas.FHe * (Pamb - PH2O);
        for (let i = 0; i < 16; i++) {
            pn[i] += (PiN2 - pn[i]) * (1 - Math.exp(-kN2[i] * dtSec));
            pe[i] += (PiHe - pe[i]) * (1 - Math.exp(-kHe[i] * dtSec));
        }
    }
}

// =============== STEP 2 — Ceiling iniziale + prima tappa ===========================
function showCeilingInfo(pn, pe) {
    const depth_m = n('#depth');
    const pressione = 1 + depth_m / 10;
    const gflow = n('#gfLow') / 100;
    const gfhi = n('#gfHigh') / 100;

    // GF info
    let GFm = (gfhi - gflow) / ((pressione - 1) * 10);
    let GF = gfhi - GFm * ((pressione - 1) * 10);
    let gffinal = Math.min(Math.max(GF, gflow), gfhi);

    // Prima tappa (semper arrotondata a SALIRE al multiplo di 3 m)
    const ceiling0_raw = ceilingGF(pn, pe, gflow);
    const ceiling0 = ceiling0_raw + FIRST_STOP_EPS;
    let primatappamax = Math.ceil(((ceiling0 - 1) * 10) / 3) * 3;
    if (primatappamax < 3) primatappamax = 3;

    let lines = [];
    lines.push(`Model: ZHL-16${currentModel()} + GF ${Math.round(gflow*100)}/${Math.round(gfhi*100)}`);
    lines.push(`GF (at current Pamb): ${gffinal.toFixed(2)}`);
    lines.push(`Ceiling: ${(((ceiling0_raw-1)*10)).toFixed(1)} m`);
    lines.push(`First stop depth: ${primatappamax} m`);
    $w('#text29').text = lines.join("\n");
}

// =============== PIANO DECO + RISALITA ALLA PRIMA TAPPA ===========================
function runDecoPlan(pn, pe) {
    const gflow = n('#gfLow') / 100,
        gfhi = n('#gfHigh') / 100;
    const gases = getGases();
    const { halftimen2, halftimehe } = getCoefficients();
    const PH2O = 0.0627;
    const { depth_m, ascRate } = getDiveParams();

    const kN2 = halftimen2.map(ht => Math.log(2) / (ht * 60));
    const kHe = halftimehe.map(ht => Math.log(2) / (ht * 60));

    function pickBestGas(depthM) {
        const Pamb = 1 + depthM / 10;
        let usable = gases.filter(g => isFinite(g.switchDepth) && depthM <= g.switchDepth);
        usable = usable.filter(g => g.FO2 * Pamb <= g.ppo2lim + 1e-6);
        if (!usable.length) return gases[0];
        usable.sort((a, b) => b.FO2 - a.FO2);
        return usable[0];
    }

    // copie tessuti
    let decopn = pn.slice(),
        decope = pe.slice();

    // prima tappa da ceiling con GF_low
    const ceiling0_raw = ceilingGF(decopn, decope, gflow);
    const ceiling0 = ceiling0_raw + FIRST_STOP_EPS;
    let primatappamax = Math.ceil(((ceiling0 - 1) * 10) / 3) * 3;
    if (primatappamax < 3) primatappamax = 3;

    // integra RISALITA fondo -> prima tappa con gas dinamico (coerente col planner)
    {
        const from = depth_m,
            to = primatappamax;
        if (ascRate > 0 && from > to) {
            const delta = from - to;
            const steps = Math.max(1, Math.ceil(delta));
            for (let i = 0; i < steps; i++) {
                const d1 = from - i;
                const d2 = from - (i + 1);
                const mid = (d1 + d2) / 2;
                const gas = pickBestGas(Math.max(0, mid));
                integrateTravelTissues(decopn, decope, kN2, kHe, gas, d1, d2, ascRate, PH2O);
            }
        }
    }

    // retta GF
    const GFmdeco = (gfhi - gflow) / primatappamax;

    let counterstep = primatappamax;
    let stops = [];

    while (counterstep > 0) {
        let GF = gfhi - GFmdeco * counterstep;
        if (GF < gflow) GF = gflow;
        if (GF > gfhi) GF = gfhi;

        const gasNow = pickBestGas(counterstep);
        const PambStop = 1 + counterstep / 10;
        const PiN2 = gasNow.FN2 * (PambStop - PH2O);
        const PiHe = gasNow.FHe * (PambStop - PH2O);

        let holdSec = 0;
        let decoceiling = ceilingGF(decopn, decope, GF);
        const nextPamb = PambStop - 0.3;
        const eps = (counterstep <= SHALLOW_THRESHOLD) ? CEIL_EPS_SHALLOW : CEIL_EPS_DEEP;

        while (decoceiling > nextPamb + eps) {
            for (let i = 0; i < 16; i++) {
                decopn[i] += (PiN2 - decopn[i]) * (1 - Math.exp(-kN2[i] * STEP_SEC));
                decope[i] += (PiHe - decope[i]) * (1 - Math.exp(-kHe[i] * STEP_SEC));
            }
            holdSec += STEP_SEC;
            decoceiling = ceilingGF(decopn, decope, GF);
        }

        const holdMin = (ROUNDING === "floor") ? Math.floor(holdSec / 60) : Math.round(holdSec / 60);
        if (holdMin > 0) {
            stops.push({ depth: counterstep, time: holdMin, GF, ceiling: decoceiling, gas: gasNow });
        }
        counterstep -= 3;
    }

    // ---- Consumi ----
    const usage = computeGasUsage(stops, gases);

    // ---- Runtime cumulativo (min) ----
    const { depth_m: D, bottomMin: BT, descRate, ascRate: AR } = getDiveParams();
    let runtimeMin = 0;
    if (isFinite(D) && descRate > 0) runtimeMin += D / descRate; // discesa
    if (isFinite(BT) && BT > 0) runtimeMin += BT; // fondo
    let rtLeaveBottom = runtimeMin; // runtime quando si lascia il fondo
    if (stops.length > 0 && AR > 0) runtimeMin += (D - stops[0].depth) / AR; // alla 1ª tappa
    const firstStopRt = runtimeMin;

    for (let i = 0; i < stops.length; i++) {
        const s = stops[i];
        runtimeMin += s.time;
        s.runtime = runtimeMin;
        if (i < stops.length - 1 && AR > 0) {
            const nextDepth = stops[i + 1].depth;
            runtimeMin += (s.depth - nextDepth) / AR;
        }
    }

    // ---- END & Gas Density (solo gas di fondo) ----
    const infoBottom = bottomGasInfo(gases[0], D);

    // ---- CNS% totale (NOAA) su discesa, fondo, risalite, soste) ----
    const cnsTotal = computeCNSPercent(stops, gases);

    // ===== Output piano (allineato, depth/time evidenziati) =====
    const DEP_W = 5,
        TIME_W = 6,
        RT_W = 6,
        GAS_W = 18,
        PPO2_W = 5;

    let rows = [];
    rows.push(spanBase(`PLAN — Single OC (ZHL-16${currentModel()} + GF ${Math.round(gflow*100)}/${Math.round(gfhi*100)})`, COLOR_BASE_TEXT));
    rows.push(spanDim(`(ppO₂ shown at stop depth)\n`, COLOR_DIM_TEXT));
    rows.push(""); // riga vuota

    // RIEPILOGO GAS DI FONDO: END & Densità
    rows.push(spanBase(`Bottom gas: ${gasDisplay(gases[0]).label}`, COLOR_BASE_TEXT));
    rows.push(spanDim(`\nEND @ ${D} m: ${infoBottom.ENDm.toFixed(0)} m | Gas density @ ${D} m: ${infoBottom.density_gL.toFixed(2)} g/L\n\n\n`, COLOR_DIM_TEXT));
    rows.push(""); // riga vuota

    // Riga "leave bottom" + runtime fino alla 1ª tappa
    if (stops.length) {
        rows.push(
            spanDim(`Leave bottom (${Math.round(rtLeaveBottom)})`, COLOR_DIM_TEXT) +
            spanBase(`\n → ascend to first stop @ `, COLOR_BASE_TEXT) +
            spanHilite(rcol(`${stops[0].depth} m`, DEP_W)) +
            spanBase(`    `, COLOR_BASE_TEXT) +
            spanDim(`(${Math.round(firstStopRt)})`, COLOR_DIM_TEXT)
        );
    }

    // Soste
    for (const s of stops) {
        const depthStr = `${s.depth} m`;
        const timeStr = `${s.time} min`;
        const PambStop = 1 + s.depth / 10;
        const ppO2 = (s.gas.FO2 * PambStop).toFixed(2);
        const runStr = `(${Math.round(s.runtime)})`;
        const gdisp = gasDisplay(s.gas);
        const gasStr = gdisp.label;

        const line =
            spanBase("\nStop @ ", COLOR_BASE_TEXT) +
            spanHilite(rcol(depthStr, DEP_W)) + spanBase("  ", COLOR_BASE_TEXT) +
            spanHilite(rcol(timeStr, TIME_W)) + spanBase("  ", COLOR_BASE_TEXT) +
            spanDim(rcol(runStr, RT_W), COLOR_DIM_TEXT) + spanBase("  ", COLOR_BASE_TEXT) +
            spanBase("--> ", COLOR_BASE_TEXT) +
            spanDim(lcol(gasStr, GAS_W), COLOR_DIM_TEXT) + spanBase("  ", COLOR_BASE_TEXT) +
            spanDim(`ppO₂ ${rcol(ppO2, PPO2_W)}`, COLOR_DIM_TEXT);

        rows.push(line);
    }

    // Consumi
    rows.push('\n' + spanBase('\nGas usage (surface liters):\n', COLOR_BASE_TEXT));
    let totalNL = 0;
    for (const it of usage) {
        totalNL += it.liters;
        const lbl = lcol(it.label, 18);
        const val = rcol(Math.round(it.liters).toString(), 8);
        rows.push(spanDim(`• ${lbl}  ${val} NL\n`, COLOR_DIM_TEXT));
    }
    rows.push(spanDim(`Total${' '.repeat(17)}${rcol(Math.round(totalNL).toString(), 8)} NL\n`, COLOR_DIM_TEXT));

    // CNS
    rows.push('');
    rows.push(spanBase(`\nCNS total: ${cnsTotal.toFixed(0)}%\n\n\n\n\n`, COLOR_BASE_TEXT));

    const html =
        `<pre style="
      margin:0; white-space:pre-wrap;
      font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, 'Courier New', monospace;
      font-size:14px; line-height:1.4; color:${COLOR_BASE_TEXT};
    ">` + rows.join("") + `</pre>`;

    if ($w('#planText').html !== undefined) $w('#planText').html = html;
    else if ($w('#planText').value !== undefined) $w('#planText').value = html;
    else $w('#planText').text = rows.map(stripTags).join("\n");

    // --- Snapshot tessuti immediatamente a superficie (Air 21/79) ---
    function renderSurfaceTissues(decopn, decope, lastStopDepth, ascRate, kN2, kHe, PH2O) {
        let pnS = decopn.slice();
        let peS = decope.slice();

        // Risalita ultima sosta -> superficie con aria (21/79)
        if (isFinite(lastStopDepth) && lastStopDepth > 0 && ascRate > 0) {
            const air = { FO2: 0.21, FHe: 0.00, FN2: 0.79 };
            integrateTravelTissues(pnS, peS, kN2, kHe, air, lastStopDepth, 0, ascRate, PH2O);
        }

        // Snapshot NOW @ surface
        let lines = [];
        lines.push("\n\n\nTissue saturation @ surface (Air 21/79)\n");
        lines.push("Idx | PN₂ (bar) | PHe (bar) | Ptot (bar)");
        for (let i = 0; i < 16; i++) {
            const PN2 = pnS[i];
            const PHe = peS[i];
            const Ptot = PN2 + PHe;
            lines.push(`${pad2(i+1)} | ${r3(PN2)} | ${r3(PHe)} | ${r3(Ptot)}`);
        }

        if ($w('#text37').text !== undefined) {
            $w('#text37').text = lines.join("\n");
        }
    }
    // --- Snapshot tessuti a superficie ---
    const lastStopDepth = (stops.length ? stops[stops.length - 1].depth : 0);
    renderSurfaceTissues(decopn, decope, lastStopDepth, AR, kN2, kHe, PH2O);

    return stops;
}

// ================= GAS (robusto a campi vuoti / EAN/O2) ============================
function getGases() {
    function _raw(id) { return String($w(id).value || '').trim(); }

    function _num(id) { const s = _raw(id).replace(',', '.'); const v = Number(s); return isFinite(v) ? v : NaN; }

    function _pct(id, def = 0) { const v = _num(id); return isFinite(v) ? v / 100 : def; }

    // usa #maxppo2 per TUTTE le miscele
    const maxppo2 = _num('#maxppo2');

    let gases = [
        { name: "Bottom", FO2: _pct('#o20', 0), FHe: _pct('#he0', 0), ppo2lim: maxppo2 },
        { name: "Deco1", FO2: _pct('#o21', 0), FHe: _pct('#he1', 0), ppo2lim: maxppo2 },
        { name: "Deco2", FO2: _pct('#o22', 0), FHe: _pct('#he2', 0), ppo2lim: maxppo2 },
        { name: "Deco3", FO2: _pct('#o23', 0), FHe: _pct('#he3', 0), ppo2lim: maxppo2 },
        { name: "Deco4", FO2: _pct('#o24', 0), FHe: _pct('#he4', 0), ppo2lim: maxppo2 }
    ];

    gases.forEach(g => {
        g.FO2 = Math.min(1, Math.max(0, isFinite(g.FO2) ? g.FO2 : 0));
        g.FHe = Math.min(1, Math.max(0, isFinite(g.FHe) ? g.FHe : 0));
        let sum = g.FO2 + g.FHe;
        if (sum > 1) {
            g.FO2 = g.FO2 / sum;
            g.FHe = g.FHe / sum;
        }
        g.FN2 = 1 - g.FO2 - g.FHe;

        if (g.FO2 > 0 && isFinite(g.ppo2lim) && g.ppo2lim > 0) {
            const PambMax = g.ppo2lim / g.FO2;
            g.switchDepth = (PambMax - 1) * 10;
        } else {
            g.switchDepth = NaN;
        }
    });
    return gases.filter(g => isFinite(g.FN2));
}

// ===================== GAS USAGE (surface liters) =================================
function getDiveParams() {
    const depth_m = n('#depth');
    const bottomMin = n('#bottomTime');
    let descRate = n('#descRate');
    let ascRate = n('#ascRate');
    const rmv = n('#rmv');
    if (!isFinite(descRate) || descRate <= 0) descRate = 20;
    if (!isFinite(ascRate) || ascRate <= 0) ascRate = 10;
    return { depth_m, bottomMin, descRate, ascRate, rmv };
}

function gasAtDepth(gases, depthM) {
    const Pamb = 1 + depthM / 10;
    let usable = gases.filter(g => isFinite(g.switchDepth) && depthM <= g.switchDepth);
    usable = usable.filter(g => g.FO2 * Pamb <= g.ppo2lim + 1e-6);
    if (!usable.length) return gases[0];
    usable.sort((a, b) => b.FO2 - a.FO2);
    return usable[0];
}

function integrateTravel(gases, fromDepth, toDepth, rate_m_per_min, rmv, accum) {
    if (!isFinite(fromDepth) || !isFinite(toDepth) || rate_m_per_min <= 0) return;
    const delta = toDepth - fromDepth,
        dist = Math.abs(delta);
    if (dist < 1e-6) return;
    const steps = Math.max(1, Math.ceil(dist));
    const stepM = delta / steps;
    const dtMin = Math.abs(stepM) / rate_m_per_min;

    for (let i = 0; i < steps; i++) {
        const midDepth = fromDepth + (i + 0.5) * stepM;
        const Pamb = 1 + Math.max(0, midDepth) / 10;
        const gas = gasAtDepth(gases, Math.max(0, midDepth));
        const key = gasKey(gas);
        const consSL = rmv * Pamb * dtMin;
        accum[key] = (accum[key] || 0) + consSL;
    }
}

function integrateHold(gases, depthM, minutes, rmv, accum) {
    if (minutes <= 0) return;
    const Pamb = 1 + depthM / 10;
    const gas = gasAtDepth(gases, depthM);
    const key = gasKey(gas);
    const cons = rmv * Pamb * minutes;
    accum[key] = (accum[key] || 0) + cons;
}

// --- integrazione consumi con GAS FORZATO (discesa e fondo) ---
function integrateTravelWithGas(gas, fromDepth, toDepth, rate_m_per_min, rmv, accum) {
    if (!isFinite(fromDepth) || !isFinite(toDepth) || rate_m_per_min <= 0) return;
    const delta = toDepth - fromDepth,
        dist = Math.abs(delta);
    if (dist < 1e-6) return;
    const steps = Math.max(1, Math.ceil(dist));
    const stepM = delta / steps;
    const dtMin = Math.abs(stepM) / rate_m_per_min;

    const key = gasKey(gas);
    for (let i = 0; i < steps; i++) {
        const midDepth = fromDepth + (i + 0.5) * stepM;
        const Pamb = 1 + Math.max(0, midDepth) / 10;
        const consSL = rmv * Pamb * dtMin;
        accum[key] = (accum[key] || 0) + consSL;
    }
}

function integrateHoldWithGas(gas, depthM, minutes, rmv, accum) {
    if (minutes <= 0) return;
    const Pamb = 1 + depthM / 10;
    const key = gasKey(gas);
    const cons = rmv * Pamb * minutes;
    accum[key] = (accum[key] || 0) + cons;
}

function gasKey(g) { return `${g.name}|${Math.round(g.FO2*100)}/${Math.round(g.FHe*100)}`; }

function gasLabelFromKey(k) {
    const [_, mix] = k.split('|');
    const [o2s, hes] = mix.split('/').map(Number);
    if (o2s === 21 && hes === 0) return 'Air';
    if (o2s === 100 && hes === 0) return 'Oxygen';
    if (hes > 0) return `Trimix ${o2s}/${hes}`;
    if (o2s > 21) return `Nitrox ${o2s}`;
    return `Gas ${mix}`;
}

function computeGasUsage(stops, gases) {
    const { depth_m, bottomMin, descRate, ascRate, rmv } = getDiveParams();
    const accum = {};
    const bottomGas = gases[0]; // forza la miscela di fondo

    // PRIMA: discesa su bottom gas
    integrateTravelWithGas(bottomGas, 0, depth_m, descRate, rmv, accum);

    // POI: fondo su bottom gas
    integrateHoldWithGas(bottomGas, depth_m, bottomMin, rmv, accum);

    // Risalita fino alla prima tappa: dinamico (switch appena è lecito)
    const firstStopDepth = (stops.length ? stops[0].depth : 3);
    integrateTravel(gases, depth_m, firstStopDepth, ascRate, rmv, accum);

    // Soste + risalite tra tappe: dinamico
    for (let i = 0; i < stops.length; i++) {
        const s = stops[i];
        integrateHold(gases, s.depth, s.time, rmv, accum);
        const nextDepth = (i < stops.length - 1) ? stops[i + 1].depth : 0;
        integrateTravel(gases, s.depth, nextDepth, ascRate, rmv, accum);
    }

    const items = Object.entries(accum).map(([k, liters]) => ({ key: k, label: gasLabelFromKey(k), liters }));
    items.sort((a, b) => a.label.localeCompare(b.label));
    return items;
}

// ===================== END & GAS DENSITY (gas di fondo) ===========================
// END (m) assumendo solo N2 come narcotico (O2 non narcotico): END = ((FN2/0.79)*(D+10))-10
function computeENDmeters(bottomGas, depth_m) {
    const FN2 = bottomGas.FN2;
    const Pamb = 1 + depth_m / 10;
    const END_ambient = (FN2 / 0.79) * Pamb; // equivalente air pressure
    return Math.max(0, (END_ambient - 1) * 10);
}

// densità mix @ 1 bar (kg/m^3) a ~20°C: He 0.1786, N2 1.2506, O2 1.331
function gasDensityAtDepth(bottomGas, depth_m) {
    const rhoHe = 0.1786,
        rhoN2 = 1.2506,
        rhoO2 = 1.3310;
    const rho1bar = bottomGas.FHe * rhoHe + bottomGas.FN2 * rhoN2 + bottomGas.FO2 * rhoO2; // kg/m3
    const Pamb = 1 + depth_m / 10;
    const rhoDepth = rho1bar * Pamb; // kg/m3
    return rhoDepth * 1.0; // kg/m3 -> kg/m3 (convertiamo dopo in g/L)
}

function bottomGasInfo(bottomGas, depth_m) {
    const ENDm = computeENDmeters(bottomGas, depth_m);
    const rho_kgm3 = gasDensityAtDepth(bottomGas, depth_m);
    const density_gL = rho_kgm3; // 1 kg/m3 = 1 g/L
    return { ENDm, density_gL };
}

// ===================== CNS NOAA ===================================================
// Tabella NOAA (minuti per 100% CNS) a vari ppO2 (bar). Linear interp. Sotto 0.5 bar = 0.
const NOAA_TABLE = [
    { pp: 1.6, min: 45 }, { pp: 1.5, min: 120 }, { pp: 1.4, min: 150 }, { pp: 1.3, min: 180 },
    { pp: 1.2, min: 210 }, { pp: 1.1, min: 240 }, { pp: 1.0, min: 300 }, { pp: 0.9, min: 360 },
    { pp: 0.8, min: 450 }, { pp: 0.7, min: 570 }, { pp: 0.6, min: 720 }, { pp: 0.5, min: 1440 }
];

function minutesFor100CNS(pp) {
    if (pp < 0.5) return Infinity;
    // clamp in range
    if (pp >= NOAA_TABLE[0].pp) return NOAA_TABLE[0].min;
    if (pp <= NOAA_TABLE[NOAA_TABLE.length - 1].pp) return NOAA_TABLE[NOAA_TABLE.length - 1].min;
    // linear interp between surrounding nodes
    for (let i = 0; i < NOAA_TABLE.length - 1; i++) {
        const a = NOAA_TABLE[i],
            b = NOAA_TABLE[i + 1];
        if (pp <= a.pp && pp >= b.pp) {
            const t = (pp - b.pp) / (a.pp - b.pp);
            return b.min + t * (a.min - b.min);
        }
    }
    return Infinity;
}

function cnsIncrement(pp, minutes) {
    const M = minutesFor100CNS(pp);
    if (!isFinite(M) || M === Infinity) return 0;
    return (minutes / M) * 100;
}
// calcolo CNS% integrando a step di 1 m durante discese/risalite + soste + fondo
function computeCNSPercent(stops, gases) {
    const { depth_m, bottomMin, descRate, ascRate } = getDiveParams();
    let cns = 0;

    // helper: CNS su travel (1 m per step)
    function cnsTravel(fromDepth, toDepth, rate_m_per_min) {
        if (!isFinite(fromDepth) || !isFinite(toDepth) || rate_m_per_min <= 0) return;
        const delta = toDepth - fromDepth,
            dist = Math.abs(delta);
        if (dist < 1e-6) return;
        const steps = Math.max(1, Math.ceil(dist));
        const stepM = delta / steps;
        const dtMin = Math.abs(stepM) / rate_m_per_min;
        for (let i = 0; i < steps; i++) {
            const midDepth = fromDepth + (i + 0.5) * stepM;
            const gas = gasAtDepth(gases, Math.max(0, midDepth));
            const ppO2 = gas.FO2 * (1 + Math.max(0, midDepth) / 10);
            cns += cnsIncrement(ppO2, dtMin);
        }
    }
    // helper: CNS su hold
    function cnsHold(depthM, minutes) {
        if (minutes <= 0) return;
        const gas = gasAtDepth(gases, depthM);
        const ppO2 = gas.FO2 * (1 + depthM / 10);
        cns += cnsIncrement(ppO2, minutes);
    }

    // 1) discesa 0->fondo (gas fondo)
    cnsTravel(0, depth_m, descRate);
    // 2) fondo
    cnsHold(depth_m, bottomMin);
    // 3) risalita al primo stop
    const firstStopDepth = (stops.length ? stops[0].depth : 3);
    cnsTravel(depth_m, firstStopDepth, ascRate);
    // 4) soste + risalite tra tappe
    for (let i = 0; i < stops.length; i++) {
        const s = stops[i];
        cnsHold(s.depth, s.time);
        const nextDepth = (i < stops.length - 1) ? stops[i + 1].depth : 0;
        cnsTravel(s.depth, nextDepth, ascRate);
    }

    return Math.max(0, cns);
}

// ============================ HELPERS =============================================
function n(id) { return Number(String($w(id).value || '').replace(',', '.')); }

function pct(id) { const v = n(id); return isFinite(v) ? v / 100 : NaN; }

function pad2(x) { return String(x).padStart(2, '0'); }

function r3(x) { return (Math.round(x * 1000) / 1000).toFixed(3); }

function rcol(s, w) { s = String(s); return (' '.repeat(w) + s).slice(-w); }

function lcol(s, w) { s = String(s); return (s + ' '.repeat(w)).slice(0, w); }

function spanBase(txt, color) { return `<span style="color:${color};">${escapeHtml(txt)}</span>`; }

function spanDim(txt, color) { return `<span style="color:${color};">${escapeHtml(txt)}</span>`; }

function spanHilite(txt) {
    return `<span style="color:${HILITE_FG}; background-color:${HILITE_BG}; padding:0 2px; border-radius:2px;">${escapeHtml(txt)}</span>`;
}

function escapeHtml(s) { return String(s).replace(/[&<>"']/g, m => ({ '&': '&amp;', '<': '&lt;', '>': '&gt;', '"': '&quot;', "'": '&#039;' } [m])); }

function stripTags(s) { return String(s).replace(/<[^>]+>/g, ''); }

function gasDisplay(g) {
    const o2 = Math.round(g.FO2 * 100),
        he = Math.round(g.FHe * 100);
    let type, label;
    if (o2 === 21 && he === 0) {
        type = 'air';
        label = 'Air';
    } else if (o2 === 100 && he === 0) {
        type = 'oxygen';
        label = 'Oxygen';
    } else if (he > 0) {
        type = 'trimix';
        label = `Trimix ${o2}/${he}`;
    } else if (o2 > 21 && he === 0) {
        type = 'nitrox';
        label = `Nitrox ${o2}`;
    } else {
        type = 'air';
        label = `Gas ${o2}/${he}`;
    }
    return { type, label, o2, he };
}

// --- Snapshot tessuti immediatamente a superficie (Air 21/79) ---
function renderSurfaceTissues(decopn, decope, lastStopDepth, ascRate, kN2, kHe, PH2O) {
    let pnS = decopn.slice();
    let peS = decope.slice();

    // Risalita ultima sosta -> superficie con aria (21/79)
    if (isFinite(lastStopDepth) && lastStopDepth > 0 && ascRate > 0) {
        const air = { FO2: 0.21, FHe: 0.00, FN2: 0.79 };
        integrateTravelTissues(pnS, peS, kN2, kHe, air, lastStopDepth, 0, ascRate, PH2O);
    }

    // Snapshot NOW @ surface
    let lines = [];
    lines.push("Tissue saturation @ surface (Air 21/79)");
    lines.push("Idx | PN₂ (bar) | PHe (bar) | Ptot (bar)");
    for (let i = 0; i < 16; i++) {
        const PN2 = pnS[i];
        const PHe = peS[i];
        const Ptot = PN2 + PHe;
        lines.push(`${pad2(i+1)} | ${r3(PN2)} | ${r3(PHe)} | ${r3(Ptot)}`);
    }

    if ($w('#text37').text !== undefined) {
        $w('#text37').text = lines.join("\n");
    }
}