@import url('https://fonts.googleapis.com/css2?family=JetBrains+Mono:wght@400;600&family=Syne:wght@400;600;700;800&family=Lato:wght@300;400;700&display=swap');

:root {
  --bg: #07080f;
  --surface: #0f1018;
  --surface2: #181924;
  --surface3: #1e1f2e;
  --border: #252637;
  --accent: #7c3aed;
  --accent2: #06b6d4;
  --accent3: #f59e0b;
  --green: #10b981;
  --pink: #ec4899;
  --text: #dde3f0;
  --muted: #5e6a80;
  --soft: #9aa3b5;
  --glow: rgba(124,58,237,0.12);
}

* { box-sizing: border-box; margin: 0; padding: 0; }

body {
  background: var(--bg);
  color: var(--text);
  font-family: 'Lato', sans-serif;
  line-height: 1.7;
  overflow-x: hidden;
}

.bg-grid {
  position: fixed; inset: 0; z-index: 0;
  background-image:
    linear-gradient(rgba(124,58,237,0.025) 1px, transparent 1px),
    linear-gradient(90deg, rgba(124,58,237,0.025) 1px, transparent 1px);
  background-size: 44px 44px;
  pointer-events: none;
}

.container { position: relative; z-index: 1; max-width: 1200px; margin: 0 auto; padding: 0 24px 80px; }

.hero { text-align: center; padding: 64px 20px 48px; }

.hero .pill {
  display: inline-block;
  background: linear-gradient(135deg, rgba(124,58,237,.25), rgba(6,182,212,.25));
  border: 1px solid rgba(124,58,237,.4);
  color: var(--accent2);
  font-family: 'JetBrains Mono', monospace;
  font-size: 11px; letter-spacing: 2px;
  padding: 5px 16px; border-radius: 100px; margin-bottom: 20px;
}

h1 {
  font-family: 'Syne', sans-serif;
  font-size: clamp(32px, 6vw, 58px);
  font-weight: 800; line-height: 1.08;
  background: linear-gradient(135deg, #ffffff 0%, #c4b5fd 50%, var(--accent2) 100%);
  -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text;
  margin-bottom: 16px;
}

.hero-sub { font-size: 17px; color: var(--soft); max-width: 600px; margin: 0 auto 32px; }

.section-label { display: flex; align-items: center; gap: 12px; margin-bottom: 20px; }

.section-num {
  width: 32px; height: 32px; border-radius: 50%;
  background: linear-gradient(135deg, var(--accent), #4f1bb5);
  display: flex; align-items: center; justify-content: center;
  font-family: 'Syne', sans-serif; font-size: 13px; font-weight: 800;
  color: #fff; flex-shrink: 0;
}

.section-title { font-family: 'Syne', sans-serif; font-size: 20px; font-weight: 700; color: #fff; }

.section-gap { margin-bottom: 32px; }

.card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: 16px; padding: 24px;
  position: relative; overflow: hidden; margin-bottom: 20px;
}

.card-accent-top::after {
  content: ''; position: absolute; top: 0; left: 0; right: 0; height: 2px;
  background: linear-gradient(90deg, var(--accent), var(--accent2));
}
.card-accent-amber::after { background: linear-gradient(90deg, var(--accent3), var(--pink)); }
.card-accent-green::after { background: linear-gradient(90deg, var(--green), var(--accent2)); }

.card-title {
  font-family: 'Syne', sans-serif; font-size: 14px; font-weight: 700;
  color: var(--accent2); text-transform: uppercase; letter-spacing: 1.5px;
  margin-bottom: 14px; display: flex; align-items: center; gap: 8px;
}

.dot { width: 7px; height: 7px; border-radius: 50%; background: currentColor; box-shadow: 0 0 6px currentColor; }

.plain-box {
  background: linear-gradient(135deg, rgba(124,58,237,0.08), rgba(6,182,212,0.05));
  border: 1px solid rgba(124,58,237,0.2);
  border-left: 3px solid var(--accent);
  border-radius: 0 10px 10px 0;
  padding: 16px 18px; margin-bottom: 14px;
}
.plain-box .plain-label {
  font-family: 'JetBrains Mono', monospace; font-size: 10px; color: var(--accent);
  letter-spacing: 2px; text-transform: uppercase; margin-bottom: 6px;
}
.plain-box p { font-size: 14px; color: var(--soft); }

.tip-box {
  background: rgba(245,158,11,0.07); border: 1px solid rgba(245,158,11,0.2);
  border-left: 3px solid var(--accent3); border-radius: 0 10px 10px 0;
  padding: 14px 16px; margin-top: 10px;
}
.tip-box .tip-label { font-size: 11px; color: var(--accent3); font-weight: 700; margin-bottom: 4px; }
.tip-box p { font-size: 13px; color: #c8a96e; }

.analogy-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); gap: 16px; margin-bottom: 24px; }

.analogy-card { background: var(--surface2); border: 1px solid var(--border); border-radius: 12px; padding: 18px; }
.analogy-icon { font-size: 32px; margin-bottom: 10px; }
.analogy-card h4 { font-family: 'Syne', sans-serif; font-size: 15px; font-weight: 700; color: #fff; margin-bottom: 6px; }
.analogy-card p { font-size: 13px; color: var(--soft); }

.step-flow { display: flex; flex-direction: column; gap: 0; }
.step-item { display: flex; gap: 16px; padding-bottom: 24px; position: relative; }
.step-item::before {
  content: ''; position: absolute; left: 19px; top: 40px;
  width: 2px; height: calc(100% - 24px);
  background: linear-gradient(to bottom, var(--border), transparent);
}
.step-item:last-child::before { display: none; }
.step-icon {
  width: 40px; height: 40px; border-radius: 50%;
  display: flex; align-items: center; justify-content: center;
  font-size: 18px; flex-shrink: 0;
  border: 2px solid var(--border); background: var(--surface2);
}
.step-content h4 { font-family: 'Syne', sans-serif; font-size: 15px; font-weight: 700; color: #fff; margin-bottom: 6px; }
.step-content p { font-size: 14px; color: var(--soft); margin-bottom: 8px; }

.formula-chip {
  display: inline-block; background: var(--surface3); border: 1px solid var(--border);
  border-radius: 6px; padding: 6px 12px;
  font-family: 'JetBrains Mono', monospace; font-size: 12px; color: var(--accent2); margin-top: 4px;
}

.grid-2 { display: grid; grid-template-columns: 1fr 1fr; gap: 20px; }
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; }
@media(max-width: 860px) { .grid-2, .grid-3 { grid-template-columns: 1fr; } }

label { font-size: 12px; color: var(--muted); display: block; margin-bottom: 6px; font-family: 'JetBrains Mono', monospace; }
.form-row { margin-bottom: 14px; }

input[type="text"], input[type="number"] {
  width: 100%; background: var(--surface2); border: 1px solid var(--border);
  border-radius: 8px; color: var(--text);
  font-family: 'JetBrains Mono', monospace; font-size: 13px; padding: 10px 14px;
  outline: none; transition: border-color 0.2s, box-shadow 0.2s;
}
input:focus { border-color: var(--accent); box-shadow: 0 0 0 3px var(--glow); }

button {
  background: linear-gradient(135deg, var(--accent), #4f1bb5); color: white; border: none;
  border-radius: 10px; font-family: 'Syne', sans-serif; font-size: 15px; font-weight: 700;
  padding: 13px 28px; cursor: pointer; transition: all 0.2s;
  letter-spacing: 0.5px; width: 100%; margin-top: 8px;
}
button:hover { transform: translateY(-2px); box-shadow: 0 10px 28px rgba(124,58,237,.45); }
button:active { transform: translateY(0); }
.btn-secondary { background: var(--surface2); border: 1px solid var(--border); font-size: 13px; padding: 10px; }
.btn-secondary:hover { background: var(--surface3); box-shadow: none; }

.stat-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 14px; margin-bottom: 20px; }
.stat-card { background: var(--surface2); border: 1px solid var(--border); border-radius: 12px; padding: 16px; text-align: center; }
.stat-value { font-family: 'Syne', sans-serif; font-size: 22px; font-weight: 800; color: var(--accent2); }
.stat-label { font-size: 11px; color: var(--muted); margin-top: 4px; font-family: 'JetBrains Mono', monospace; }

.log-box {
  background: var(--surface2); border: 1px solid var(--border); border-radius: 10px;
  padding: 14px; font-family: 'JetBrains Mono', monospace; font-size: 11px;
  line-height: 2; max-height: 180px; overflow-y: auto; color: var(--muted);
}
.log-ok { color: var(--green); }
.log-info { color: var(--accent2); }

.progress-bar { height: 3px; background: var(--border); border-radius: 2px; margin-top: 12px; overflow: hidden; }
.progress-fill { height: 100%; background: linear-gradient(90deg, var(--accent), var(--accent2)); border-radius: 2px; transition: width 0.3s; }

.matrix-wrap { overflow-x: auto; }
table { width: 100%; border-collapse: collapse; font-size: 12px; font-family: 'JetBrains Mono', monospace; }
th { background: var(--surface2); color: var(--muted); padding: 8px 10px; text-align: center; font-weight: 600; border-bottom: 1px solid var(--border); }
td { padding: 8px 10px; text-align: center; border-bottom: 1px solid rgba(255,255,255,0.02); }
tr:hover td { background: rgba(124,58,237,0.04); }
.heat-cell { display: inline-block; min-width: 58px; padding: 4px 8px; border-radius: 5px; font-weight: 600; }

canvas { max-width: 100%; }
/* ══ StateTransitionDiagram — dark theme (gabsgj library) ══════ */

/* ── Canvas ── */
.std-canvas, .hmm-canvas {
    position: relative;
    width: 100%;
    min-height: 420px;
    border-radius: 12px;
    background: linear-gradient(170deg, #0c0d18 0%, #111220 100%);
    overflow-x: auto;
    overflow-y: hidden;
    border: 1px solid var(--border);
    transition: background 0.5s;
}
.std-canvas svg, .hmm-canvas svg { display: block; min-width: 100%; height: 100%; }

/* 3D mode */
.std-canvas.view-3d, .hmm-canvas.view-3d {
    perspective: 1500px;
    overflow: visible;
    background: linear-gradient(170deg, #0a0b15 0%, #0f1022 100%);
}
.std-canvas.view-3d svg, .hmm-canvas.view-3d svg {
    transform-style: preserve-3d;
    transform: rotateX(55deg) rotateZ(-15deg) scale(0.75) translateY(-50px);
    transition: transform 0.8s cubic-bezier(0.2, 0.8, 0.2, 1);
}
.std-canvas.view-3d .layer-1, .hmm-canvas.view-3d .layer-1 { transform: translateZ(120px); }
.std-canvas.view-3d .layer-2, .hmm-canvas.view-3d .layer-2 { transform: translateZ(60px); }
.std-canvas.view-3d .layer-3, .hmm-canvas.view-3d .layer-3 { transform: translateZ(0px); }
.std-canvas.view-3d .layer-4, .hmm-canvas.view-3d .layer-4 { transform: translateZ(-80px); }
.layer-1, .layer-2, .layer-3, .layer-4 { transition: transform 0.8s; }

/* ── Replay control bar ── */
.std-controls, .hmm-controls {
    display: flex;
    align-items: center;
    gap: 6px;
    padding: 8px 12px;
    background: var(--surface2);
    border: 1px solid var(--border);
    border-radius: 8px;
    margin-bottom: 12px;
}

/* ── Buttons ── */
.std-ctrl-btn, .hmm-ctrl-btn {
    width: 32px; height: 32px;
    display: inline-flex; align-items: center; justify-content: center;
    border: 1px solid var(--border);
    border-radius: 6px;
    background: var(--surface3);
    color: var(--soft);
    font-size: 14px; cursor: pointer;
    transition: all 0.15s;
}
.std-ctrl-btn:hover:not(:disabled), .hmm-ctrl-btn:hover:not(:disabled) {
    background: rgba(124,58,237,0.15);
    border-color: var(--accent);
    color: #c4b5fd;
}
.std-ctrl-btn:disabled, .hmm-ctrl-btn:disabled { opacity: 0.3; cursor: default; }
.std-ctrl-btn.active, .hmm-ctrl-btn.active {
    background: rgba(124,58,237,0.22);
    border-color: var(--accent);
    color: #c4b5fd;
    box-shadow: 0 0 8px rgba(124,58,237,0.3);
}

/* ── Speed dropdown ── */
.std-speed-select, .hmm-speed-select {
    padding: 4px 6px;
    border-radius: 6px;
    border: 1px solid var(--border);
    background: var(--surface3);
    color: var(--soft);
    font-size: 12px; cursor: pointer;
    font-family: 'JetBrains Mono', monospace;
}
.std-speed-select:focus, .hmm-speed-select:focus {
    outline: none;
    border-color: var(--accent);
}

/* ── Timeline scrubber ── */
.std-timeline, .hmm-timeline {
    flex: 1;
    min-width: 80px;
    height: 20px;
    -webkit-appearance: none; appearance: none;
    background: transparent;
    cursor: pointer;
    margin: 0 4px;
    touch-action: none;
    user-select: none;
}
.std-timeline::-webkit-slider-runnable-track, .hmm-timeline::-webkit-slider-runnable-track {
    height: 6px; border-radius: 3px;
    background: linear-gradient(to right, var(--accent) var(--progress, 0%), var(--border) var(--progress, 0%));
}
.std-timeline::-moz-range-track, .hmm-timeline::-moz-range-track {
    height: 6px; border-radius: 3px;
    background: linear-gradient(to right, var(--accent) var(--progress, 0%), var(--border) var(--progress, 0%));
    border: none;
}
.std-timeline::-webkit-slider-thumb, .hmm-timeline::-webkit-slider-thumb {
    -webkit-appearance: none;
    width: 16px; height: 16px; border-radius: 50%;
    background: var(--accent);
    border: 2px solid var(--surface);
    box-shadow: 0 0 8px rgba(124,58,237,0.55);
    cursor: grab; margin-top: -5px;
}
.std-timeline::-moz-range-thumb, .hmm-timeline::-moz-range-thumb {
    width: 14px; height: 14px; border-radius: 50%;
    background: var(--accent);
    border: 2px solid var(--surface);
    cursor: grab;
}

/* ── Labels ── */
.std-iter-label, .hmm-iter-label {
    font-family: 'JetBrains Mono', monospace;
    font-size: 11px; color: var(--muted);
    white-space: nowrap; min-width: 80px; text-align: center;
}
.std-mode-label, .hmm-mode-label {
    font-family: 'JetBrains Mono', monospace;
    font-size: 10px; color: var(--muted);
    white-space: nowrap; min-width: 42px;
}

/* ── Inspector panel ── */
.std-inspector, .hmm-inspector {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.3s ease, padding 0.3s ease;
    background: var(--surface2);
    border-radius: 10px;
    border: 1px solid transparent;
    padding: 0 14px;
    font-size: 12px;
}
.std-inspector.visible, .hmm-inspector.visible {
    max-height: 600px;
    padding: 14px;
    border-color: var(--border);
    margin-top: 12px;
}
.std-inspector h4, .hmm-inspector h4 {
    margin: 0 0 10px;
    font-size: 13px; font-weight: 700;
    color: #e2e8f0;
    font-family: 'Syne', sans-serif;
}
.std-inspector table, .hmm-inspector table {
    border-collapse: collapse;
    font-family: 'JetBrains Mono', monospace;
    font-size: 11px; margin-bottom: 10px; width: 100%;
}
.std-inspector th, .std-inspector td,
.hmm-inspector th, .hmm-inspector td {
    border: 1px solid var(--border);
    padding: 4px 8px; text-align: center;
}
.std-inspector th, .hmm-inspector th {
    background: var(--surface3);
    font-weight: 600; color: var(--muted);
}
.std-inspector td, .hmm-inspector td { color: var(--soft); }
.std-inspector strong, .hmm-inspector strong { color: var(--soft); }

/* ── Particle glow ── */
@keyframes particle-glow { 0%, 100% { opacity: 0.6; } 50% { opacity: 1; } }

/* ── Fullscreen ── */
#diagram-card:fullscreen,
#diagram-card:-webkit-full-screen {
    background: var(--bg);
    padding: 24px;
    display: flex; flex-direction: column;
    overflow: hidden;
    width: 100vw; height: 100vh;
}
#diagram-card:fullscreen .std-canvas,
#diagram-card:fullscreen .hmm-canvas,
#diagram-card:-webkit-full-screen .std-canvas,
#diagram-card:-webkit-full-screen .hmm-canvas {
    flex: 1 1 0%; min-height: 0;
    height: auto !important;
    overflow: hidden;
    display: flex; align-items: center; justify-content: center;
}
#diagram-card:fullscreen .std-canvas svg,
#diagram-card:fullscreen .hmm-canvas svg,
#diagram-card:-webkit-full-screen .std-canvas svg,
#diagram-card:-webkit-full-screen .hmm-canvas svg {
    width: 100% !important; height: 100% !important;
    max-width: 100%; max-height: 100%;
}
#diagram-card:fullscreen .std-controls,
#diagram-card:fullscreen .hmm-controls,
#diagram-card:-webkit-full-screen .std-controls,
#diagram-card:-webkit-full-screen .hmm-controls {
    flex-shrink: 0; margin-top: 10px;
}
#diagram-card:fullscreen .std-inspector,
#diagram-card:fullscreen .hmm-inspector,
#diagram-card:-webkit-full-screen .std-inspector,
#diagram-card:-webkit-full-screen .hmm-inspector {
    flex-shrink: 0; max-height: 200px; overflow-y: auto;
}

/* ── Mobile ── */
@media (max-width: 640px) {
    .std-controls, .hmm-controls { flex-wrap: wrap; gap: 4px; padding: 4px 6px; }
    .std-canvas, .hmm-canvas { min-height: 300px; }
    .std-timeline, .hmm-timeline { min-width: 100%; order: 20; }
    .std-iter-label, .hmm-iter-label { min-width: auto; font-size: 10px; order: 21; }
    .std-ctrl-btn, .hmm-ctrl-btn { width: 28px; height: 28px; font-size: 12px; }
    .std-speed-select, .hmm-speed-select { font-size: 11px; padding: 2px 4px; }
    .std-inspector table, .hmm-inspector table { font-size: 9px; }
    .std-inspector th, .std-inspector td,
    .hmm-inspector th, .hmm-inspector td { padding: 2px 4px; }
}

.converged { color: var(--green); font-weight: 800; }
.not-converged { color: var(--accent3); }

.divider { border: none; border-top: 1px solid var(--border); margin: 36px 0; }

.glossary-item {
  padding: 14px 0; border-bottom: 1px solid rgba(255,255,255,0.04);
  display: grid; grid-template-columns: 150px 1fr; gap: 16px; align-items: start;
}
.glossary-item:last-child { border-bottom: none; }
.glossary-term { font-family: 'JetBrains Mono', monospace; font-size: 13px; color: var(--accent2); font-weight: 600; }
.glossary-def { font-size: 13px; color: var(--soft); }

.highlight { color: var(--accent3); font-weight: 700; }
.hl-green { color: var(--green); font-weight: 700; }
.hl-cyan { color: var(--accent2); font-weight: 700; }
.hl-pink { color: var(--pink); font-weight: 700; }

::-webkit-scrollbar { width: 6px; height: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: var(--border); border-radius: 3px; }

.explain-box {
  background: rgba(16,185,129,0.06); border: 1px solid rgba(16,185,129,0.18);
  border-left: 3px solid var(--green); border-radius: 0 10px 10px 0;
  padding: 14px 16px; margin-top: 16px;
}
.explain-box .explain-label {
  font-size: 11px; color: var(--green); font-family: 'JetBrains Mono';
  letter-spacing: 1.5px; text-transform: uppercase; margin-bottom: 6px;
}
.explain-box p { font-size: 13px; color: #7dd3b8; }