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<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8" />
    <title>d20 — Fixed Render + Weighted/Fair Roll</title>
    <meta name="viewport" content="width=device-width, initial-scale=1" />
    <style>
        :root { --bg:#0b1020; --panel:#121a33; --text:#e6e9f2; --accent:#7dd3fc; }
        * { box-sizing: border-box; }
        html, body { height: 100%; }
        body {
            margin: 0;
            color: var(--text);
            background: #0b1020;
            font-family: ui-sans-serif, system-ui, -apple-system, Segoe UI, Roboto, Arial;
            display: flex;
            flex-direction: column;
            gap: 14px;
            align-items: center;
            padding: 14px;
        }
        h1 { margin: 8px 0 0; font-weight: 600; font-size: 20px; }
        .wrap {
            width: min(1100px, 95vw);
            display: grid;
            grid-template-columns: 1.2fr 0.8fr;
            gap: 14px;
        }
        #stage {
            width: 100%;
            height: 60vh;
            min-height: 380px;
            background: #04070f;
            border: 1px solid #1f2b53;
            border-radius: 14px;
            overflow: hidden;
            position: relative;
        }
        #ui {
            background: var(--panel);
            border: 1px solid #1f2b53;
            border-radius: 14px;
            padding: 14px;
            display: flex;
            flex-direction: column;
            gap: 12px;
        }
        .row {
            display: grid;
            grid-template-columns: 1fr 1fr;
            gap: 10px;
        }
        label { font-size: 12px; color: #b9c2dc; }
        input[type="number"],
        input[type="range"] {
            width: 100%;
            background: #0e152b;
            color: var(--text);
            border: 1px solid #243266;
            border-radius: 10px;
            padding: 8px 10px;
            outline: none;
        }
        input[type="range"] { height: 32px; }
        .switch {
            display: flex;
            align-items: center;
            gap: 8px;
            font-size: 13px;
        }
        button {
            padding: 10px 14px;
            border-radius: 12px;
            cursor: pointer;
            background: linear-gradient(180deg, #1d4ed8, #1e40af);
            color: white;
            font-weight: 600;
            border: 1px solid #203986;
            box-shadow: 0 6px 20px #1d4ed84d;
        }
        button:active { transform: translateY(1px); }
        .readout {
            display: grid;
            grid-template-columns: repeat(3, 1fr);
            gap: 8px;
            text-align: center;
            background: #0e152b;
            border: 1px solid #243266;
            border-radius: 12px;
            padding: 10px;
            font-variant-numeric: tabular-nums;
        }
        .badge { font-size: 12px; color: #9fb3ff; }
        #chartBox {
            background: #0e152b;
            border: 1px solid #243266;
            border-radius: 14px;
            padding: 10px;
        }
        #hist { width: 100%; height: 220px; display: block; }
        .tiny { font-size: 11px; color: #98a2c7; }
        .note { font-size: 12px; color: #bcd0ff; }
        @media (max-width: 800px) {
            .wrap { grid-template-columns: 1fr; }
        }
    </style>
</head>
<body>
    <h1>d20 Roll (Weighted or Fair)</h1>

    <div class="wrap">
        <div id="stage"></div>

        <div id="ui">
            <div class="switch">
                <input id="useWeight" type="checkbox" checked />
                <label for="useWeight">Use Gaussian weighting</label>
            </div>

            <div class="row">
                <div>
                    <label for="mu">Center face (μ, 1–20)</label>
                    <input id="mu" type="number" min="1" max="20" step="1" value="10" />
                </div>
                <div>
                    <label for="sigma">Spread (σ, 0.3–8)</label>
                    <input id="sigma" type="number" min="0.3" max="8" step="0.1" value="2.5" />
                </div>
            </div>

            <div class="row">
                <div>
                    <label for="spin">Spin time (sec)</label>
                    <input id="spin" type="range" min="0.6" max="2.8" step="0.1" value="1.6" />
                </div>
                <div>
                    <label for="bounciness">Bounciness</label>
                    <input id="bounciness" type="range" min="0" max="1" step="0.05" value="0.35" />
                </div>
            </div>

            <button id="rollBtn">🎲 Roll d20</button>

            <div class="readout">
                <div><div class="badge">Last Roll</div><div id="lastRoll" style="font-size:26px; font-weight:700;"></div></div>
                <div><div class="badge">Total Rolls</div><div id="totalRolls" style="font-size:22px; font-weight:700;">0</div></div>
                <div><div class="badge">Expected Center</div><div id="expect" style="font-size:22px; font-weight:700;">10</div></div>
            </div>

            <div id="chartBox">
                <canvas id="hist" width="480" height="220"></canvas>
                <div class="tiny">Histogram of faces 1..20. Dotted curve = current Gaussian (scaled). Turn off “Use Gaussian weighting” for a fair die.</div>
            </div>

            <div class="note">If nothing appears, press F12 → Console and tell me any red errors you see.</div>
        </div>
    </div>

    <script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/r152/three.min.js"></script>
    <script>
        document.addEventListener('DOMContentLoaded', () => {
            // ----- Safety: WebGL support -----
            if (!window.WebGLRenderingContext) {
                alert('WebGL not supported in this browser.');
                return;
            }

            // ---------- Gaussian + sampling ----------
            function gaussianWeights(n, mu, sigma) {
                const w = new Array(n);
                const s2 = sigma * sigma * 2;
                let sum = 0;
                for (let i = 1; i <= n; i++) {
                    const val = Math.exp(-((i - mu) * (i - mu)) / s2);
                    w[i - 1] = val;
                    sum += val;
                }
                for (let i = 0; i < n; i++) w[i] /= sum;
                return w;
            }
            function sampleDiscrete(weights) {
                const r = Math.random();
                let acc = 0;
                for (let i = 0; i < weights.length; i++) {
                    acc += weights[i];
                    if (r <= acc) return i;
                }
                return weights.length - 1;
            }

            // ---------- Histogram ----------
            const histCanvas = document.getElementById('hist');
            const hctx = histCanvas.getContext('2d');
            let counts = Array(20).fill(0);
            let totalRolls = 0;
            function drawHistogram(gauss) {
                const w = histCanvas.width, h = histCanvas.height;
                hctx.clearRect(0, 0, w, h);
                const padL = 28, padR = 10, padT = 10, padB = 20;
                const chartW = w - padL - padR, chartH = h - padT - padB;
                hctx.strokeStyle = '#3a4a7d';
                hctx.lineWidth = 1;
                hctx.beginPath();
                hctx.moveTo(padL, padT);
                hctx.lineTo(padL, padT + chartH);
                hctx.lineTo(padL + chartW, padT + chartH);
                hctx.stroke();

                const maxCount = Math.max(1, ...counts);
                const yScale = (v) => padT + chartH - (v / maxCount) * chartH;

                const n = 20, barGap = 2, barW = (chartW / n) - barGap;
                for (let i = 0; i < n; i++) {
                    const x = padL + i * (chartW / n) + barGap / 2;
                    const y = yScale(counts[i]);
                    hctx.fillStyle = '#7dd3fc';
                    hctx.fillRect(x, y, barW, (padT + chartH) - y);
                    hctx.fillStyle = '#9fb3ff';
                    hctx.font = '10px system-ui';
                    hctx.textAlign = 'center';
                    hctx.fillText(String(i + 1), x + barW / 2, padT + chartH + 12);
                }
                if (gauss) {
                    hctx.beginPath();
                    for (let i = 0; i < n; i++) {
                        const x = padL + i * (chartW / n) + (chartW / n) / 2;
                        const y = yScale(gauss[i] * maxCount);
                        if (i === 0) hctx.moveTo(x, y);
                        else hctx.lineTo(x, y);
                    }
                    hctx.strokeStyle = '#94a3b8';
                    hctx.setLineDash([4, 4]);
                    hctx.lineWidth = 1.5;
                    hctx.stroke();
                    hctx.setLineDash([]);
                }
            }

            // ---------- Three.js scene ----------
            const stage = document.getElementById('stage');
            const renderer = new THREE.WebGLRenderer({ antialias: true, alpha: false });
            renderer.setClearColor(0x0a0f1d, 1);
            renderer.shadowMap.enabled = true;
            renderer.shadowMap.type = THREE.PCFSoftShadowMap;
            stage.appendChild(renderer.domElement);

            const scene = new THREE.Scene();
            const camera = new THREE.PerspectiveCamera(45, 1, 0.1, 100);
            camera.position.set(0, 2.6, 5.2);
            camera.lookAt(0, 0, 0);

            const hemi = new THREE.HemisphereLight(0x9fcfff, 0x203050, 0.9);
            scene.add(hemi);
            const dir = new THREE.DirectionalLight(0xffffff, 1.1);
            dir.position.set(3, 4, 2);
            dir.castShadow = true;
            scene.add(dir);

            const grid = new THREE.GridHelper(20, 20, 0x2953ff, 0x1f2b53);
            grid.position.y = -1.05;
            scene.add(grid);

            const ground = new THREE.Mesh(
                new THREE.CircleGeometry(8, 64),
                new THREE.MeshStandardMaterial({ color: 0x0b1226, roughness: 0.95, metalness: 0.0 })
            );
            ground.rotation.x = -Math.PI / 2;
            ground.receiveShadow = true;
            scene.add(ground);

            const geo = new THREE.IcosahedronGeometry(1, 0);
            const mat = new THREE.MeshStandardMaterial({ color: 0x1f4fff, metalness: 0.35, roughness: 0.4 });
            const d20 = new THREE.Mesh(geo, mat);
            d20.castShadow = true;
            scene.add(d20);

            geo.computeVertexNormals();
            const pos = geo.attributes.position, index = geo.index;
            const faceInfo = [];
            const vA = new THREE.Vector3(), vB = new THREE.Vector3(), vC = new THREE.Vector3();
            const cb = new THREE.Vector3(), ab = new THREE.Vector3();

            for (let i = 0; i < index.count; i += 3) {
                const a = index.getX(i), b = index.getX(i + 1), c = index.getX(i + 2);
                vA.fromBufferAttribute(pos, a);
                vB.fromBufferAttribute(pos, b);
                vC.fromBufferAttribute(pos, c);
                const center = new THREE.Vector3().addVectors(vA, vB).add(vC).multiplyScalar(1 / 3);
                cb.subVectors(vC, vB);
                ab.subVectors(vA, vB);
                const normal = new THREE.Vector3().crossVectors(cb, ab).normalize();
                faceInfo.push({ center, normal, number: faceInfo.length + 1 });
            }
            d20.rotation.set(0.8, 0.4, 0.2);

            const loader = new THREE.FontLoader();
            loader.load('https://threejs.org/examples/fonts/helvetiker_regular.typeface.json', (font) => {
                const textMaterial = new THREE.MeshBasicMaterial({ color: 0xe6e9f2 });
                for (let i = 0; i < faceInfo.length; i++) {
                    const textGeo = new THREE.TextGeometry(String(i + 1), {
                        font: font,
                        size: 0.25,
                        height: 0.05,
                    });
                    textGeo.computeBoundingBox();
                    const centerOffset = -0.5 * (textGeo.boundingBox.max.x - textGeo.boundingBox.min.x);
                    textGeo.translate(centerOffset, 0, 0);

                    const textMesh = new THREE.Mesh(textGeo, textMaterial);
                    const face = faceInfo[i];
                    textMesh.position.copy(face.center).multiplyScalar(1.01);
                    const up = new THREE.Vector3(0, 1, 0);
                    const normal = face.normal;
                    const axis = new THREE.Vector3().crossVectors(up, normal).normalize();
                    const angle = Math.acos(up.dot(normal));
                    textMesh.quaternion.setFromAxisAngle(axis, angle);
                    d20.add(textMesh);
                }
            });

            // ----- sizing -----
            function sizeRenderer() {
                const w = stage.clientWidth || 800;
                const h = stage.clientHeight || 450;
                renderer.setPixelRatio(Math.min(window.devicePixelRatio, 2));
                renderer.setSize(w, h, false);
                camera.aspect = w / h;
                camera.updateProjectionMatrix();
            }
            sizeRenderer();
            window.addEventListener('resize', sizeRenderer);

            // ---------- Animation helpers ----------
            let isRolling = false;
            function easeOutCubic(t) { return 1 - Math.pow(1 - t, 3); }
            function targetQuaternionForFace(faceIdx) {
                const currentQ = d20.quaternion.clone();
                const up = new THREE.Vector3(0, 1, 0);
                const localNormal = faceInfo[faceIdx].normal.clone();
                const worldNormal = localNormal.clone().applyQuaternion(currentQ);
                const deltaQ = new THREE.Quaternion().setFromUnitVectors(worldNormal, up);
                const yaw = new THREE.Quaternion().setFromAxisAngle(up, Math.random() * Math.PI * 2);
                return yaw.multiply(deltaQ).multiply(currentQ).normalize();
            }
            function randomTumble() {
                const axis = new THREE.Vector3(Math.random() * 2 - 1, Math.random() * 2 - 1, Math.random() * 2 - 1).normalize();
                const angle = (Math.PI * 2) * (1 + Math.random() * 2);
                const q = new THREE.Quaternion().setFromAxisAngle(axis, angle);
                d20.quaternion.multiply(q);
            }
            function animateToQuaternion(targetQ, durationSec, bounciness, onDone) {
                const startQ = d20.quaternion.clone();
                const start = performance.now();
                const dur = durationSec * 1000;
                function frame(now) {
                    const t = Math.min(1, (now - start) / dur);
                    const e = easeOutCubic(t);
                    THREE.Quaternion.slerp(startQ, targetQ, d20.quaternion, e);
                    if (bounciness > 0 && t > 0.7) {
                        const wob = (1 - e) * bounciness * 0.15;
                        d20.quaternion.multiply(new THREE.Quaternion().setFromAxisAngle(new THREE.Vector3(1, 0, 0), wob * Math.sin(20 * t)));
                    }
                    if (t < 1) {
                        requestAnimationFrame(frame);
                    } else {
                        isRolling = false;
                        onDone && onDone();
                    }
                }
                requestAnimationFrame(frame);
            }

            // ---------- UI / Roll ----------
            const muEl = document.getElementById('mu');
            const sigmaEl = document.getElementById('sigma');
            const useWeightEl = document.getElementById('useWeight');
            const spinEl = document.getElementById('spin');
            const bounceEl = document.getElementById('bounciness');
            const rollBtn = document.getElementById('rollBtn');
            const lastRollEl = document.getElementById('lastRoll');
            const totalEl = document.getElementById('totalRolls');
            const expectEl = document.getElementById('expect');

            // histogram init
            function clamp(v, lo, hi) { return Math.max(lo, Math.min(hi, v)); }
            function currentWeights() {
                if (!useWeightEl.checked) return Array(20).fill(1 / 20);
                const mu = clamp(parseInt(muEl.value || '10', 10), 1, 20);
                const sigma = clamp(parseFloat(sigmaEl.value || '2.5'), 0.3, 8.0);
                return gaussianWeights(20, mu, sigma);
            }
            function doRoll() {
                if (isRolling) return;
                isRolling = true;
                const mu = clamp(parseInt(muEl.value || '10', 10), 1, 20);
                const sigma = clamp(parseFloat(sigmaEl.value || '2.5'), 0.3, 8.0);
                expectEl.textContent = useWeightEl.checked ? String(mu) : '—';
                const weights = currentWeights();
                randomTumble();
                const faceIdx = sampleDiscrete(weights);
                const qTarget = targetQuaternionForFace(faceIdx);
                const spinSec = parseFloat(spinEl.value || '1.6');
                const bouncy = parseFloat(bounceEl.value || '0.35');
                animateToQuaternion(qTarget, spinSec, bouncy, () => {
                    const rolledNumber = faceInfo[faceIdx].number;
                    counts[rolledNumber - 1] += 1;
                    totalRolls += 1;
                    lastRollEl.textContent = rolledNumber;
                    totalEl.textContent = totalRolls;
                    drawHistogram(useWeightEl.checked ? weights : null);
                });
            }
            rollBtn.addEventListener('click', doRoll);

            muEl.addEventListener('change', () => {
                muEl.value = clamp(parseInt(muEl.value || '10', 10), 1, 20);
                drawHistogram(useWeightEl.checked ? gaussianWeights(20, parseInt(muEl.value, 10), parseFloat(sigmaEl.value || '2.5')) : null);
                expectEl.textContent = useWeightEl.checked ? muEl.value : '—';
            });
            sigmaEl.addEventListener('change', () => {
                sigmaEl.value = clamp(parseFloat(sigmaEl.value || '2.5'), 0.3, 8.0);
                drawHistogram(useWeightEl.checked ? gaussianWeights(20, parseInt(muEl.value || '10', 10), parseFloat(sigmaEl.value)) : null);
            });
            useWeightEl.addEventListener('change', () => {
                drawHistogram(useWeightEl.checked ? gaussianWeights(20, parseInt(muEl.value || '10', 10), parseFloat(sigmaEl.value || '2.5')) : null);
                expectEl.textContent = useWeightEl.checked ? (muEl.value || '10') : '—';
            });

            drawHistogram(gaussianWeights(20, parseInt(muEl.value || '10', 10), parseFloat(sigmaEl.value || '2.5')));

            // ---------- Render loop ----------
            function tick() {
                if (!isRolling) d20.rotation.y += 0.0025;
                renderer.render(scene, camera);
                requestAnimationFrame(tick);
            }
            sizeRenderer();
            tick();

            window.addEventListener('error', e => console.log('Error:', e.message));
        });
    </script>
</body>
</html>