/* Dark mode is the default; light mode follows the browser preference below. */
:root {
  color-scheme: light dark;
  --bg: #0b0d10;
  --bg-alt: #111418;
  --panel: #161a20;
  --border: #232932;
  --text: #e6e8eb;
  --text-dim: #9aa3ad;
  --accent: #7cc4ff;
  --accent-2: #b3f5a8;
  --warning: #ffcc66;
  --hero-glow: rgba(124, 196, 255, 0.08);
  --btn-primary-fg: #0a1218;
  --btn-primary-bg: var(--accent);
  --btn-primary-bg-hover: #a3d5ff;
  --runner-bg: #000;
  --terminal-bg: #000000;
  --terminal-fg: #e6e8eb;
  --mono: ui-monospace, "SF Mono", "JetBrains Mono", Menlo, Consolas, monospace;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Inter, system-ui, sans-serif;
}

@media (prefers-color-scheme: light) {
  :root {
    --bg: #fafafa;
    --bg-alt: #f1f3f5;
    --panel: #ffffff;
    --border: #e2e5ea;
    --text: #1a1d22;
    --text-dim: #6a7280;
    --accent: #0066cc;
    --accent-2: #2f8f3f;
    --warning: #b07000;
    --hero-glow: rgba(0, 102, 204, 0.07);
    --btn-primary-fg: #ffffff;
    --btn-primary-bg: var(--accent);
    --btn-primary-bg-hover: #1a78d6;
    --runner-bg: #ffffff;
    --terminal-bg: #fdf6e3;
    --terminal-fg: #586e75;
  }
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

code {
  font-family: var(--mono);
  font-size: 0.9em;
  background: var(--panel);
  padding: 0.1em 0.35em;
  border-radius: 3px;
}

.container {
  max-width: 920px;
  margin: 0 auto;
  padding: 0 24px;
}

/* ---- Hero ---- */

.hero {
  padding: 80px 0 60px;
  border-bottom: 1px solid var(--border);
  background:
    radial-gradient(ellipse 800px 400px at 50% -100px, var(--hero-glow), transparent),
    var(--bg);
}

.eyebrow {
  font-family: var(--mono);
  font-size: 13px;
  color: var(--text-dim);
  margin: 0 0 8px;
  letter-spacing: 0.02em;
}

.hero h1 {
  font-family: var(--mono);
  font-size: 56px;
  font-weight: 700;
  margin: 0 0 16px;
  letter-spacing: -0.02em;
}

.tagline {
  font-size: 18px;
  max-width: 680px;
  color: var(--text);
  margin: 0 0 32px;
}

.tagline strong { color: var(--accent-2); font-weight: 600; }

.actions {
  display: flex;
  gap: 12px;
  margin-bottom: 40px;
  flex-wrap: wrap;
}

.btn {
  display: inline-block;
  padding: 10px 18px;
  border: 1px solid var(--border);
  border-radius: 6px;
  color: var(--text);
  font-family: var(--mono);
  font-size: 14px;
  cursor: pointer;
  background: transparent;
  transition: border-color 0.15s, background 0.15s;
  text-decoration: none;
}

.btn:hover { border-color: var(--accent); text-decoration: none; }

.btn-primary {
  background: var(--btn-primary-bg);
  color: var(--btn-primary-fg);
  border-color: var(--btn-primary-bg);
  font-weight: 600;
}

.btn-primary:hover {
  background: var(--btn-primary-bg-hover);
  border-color: var(--btn-primary-bg-hover);
}

.stats {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  gap: 32px;
  flex-wrap: wrap;
  font-family: var(--mono);
  font-size: 14px;
  color: var(--text-dim);
}

.stats li strong {
  color: var(--accent-2);
  font-size: 20px;
  font-weight: 600;
  margin-right: 6px;
}

/* ---- Section ---- */

.section {
  padding: 64px 0;
  border-bottom: 1px solid var(--border);
}

.section-alt { background: var(--bg-alt); }

.section h2 {
  font-family: var(--mono);
  font-size: 28px;
  margin: 0 0 12px;
  letter-spacing: -0.01em;
}

.lede {
  color: var(--text-dim);
  font-size: 16px;
  margin: 0 0 28px;
  max-width: 680px;
}

/* ---- Asciinema tabs ---- */

.tabs {
  display: flex;
  gap: 4px;
  margin-bottom: 16px;
  flex-wrap: wrap;
}

.tab {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text-dim);
  padding: 8px 14px;
  font-family: var(--mono);
  font-size: 13px;
  border-radius: 6px;
  cursor: pointer;
  transition: color 0.15s, border-color 0.15s, background 0.15s;
}

.tab:hover { color: var(--text); border-color: var(--accent); }

.tab-active {
  color: var(--btn-primary-fg);
  background: var(--accent);
  border-color: var(--accent);
  font-weight: 600;
}

.player {
  border: 1px solid var(--border);
  border-radius: 8px;
  overflow: hidden;
  background: var(--runner-bg);
}

.caption {
  margin-top: 18px;
  font-family: var(--mono);
  font-size: 13px;
  color: var(--text-dim);
}

.caption summary {
  cursor: pointer;
  padding: 6px 0;
  color: var(--accent);
}

.caption ul { padding-left: 18px; }

.caption li { margin: 6px 0; }

.caption strong { color: var(--text); font-weight: 600; }

/* ---- Runner / xterm.js ---- */

.runner {
  border: 1px solid var(--border);
  border-radius: 8px;
  overflow: hidden;
  background: var(--runner-bg);
}

.runner-controls {
  display: flex;
  gap: 6px;
  padding: 10px;
  background: var(--panel);
  border-bottom: 1px solid var(--border);
  flex-wrap: wrap;
  align-items: center;
}

.btn-run {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text);
  padding: 6px 12px;
  font-family: var(--mono);
  font-size: 12px;
  border-radius: 4px;
  cursor: pointer;
  transition: border-color 0.15s, background 0.15s, color 0.15s;
}

.btn-run:hover:not(:disabled) {
  border-color: var(--accent);
  background: var(--hero-glow);
}

.btn-run:disabled {
  opacity: 0.4;
  cursor: wait;
}

.btn-stop {
  margin-left: auto;
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text-dim);
  padding: 6px 12px;
  font-family: var(--mono);
  font-size: 12px;
  border-radius: 4px;
  cursor: pointer;
  transition: color 0.15s, border-color 0.15s, background 0.15s;
}

.btn-stop:hover:not(:disabled) {
  color: #ff6b6b;
  border-color: #ff6b6b;
}

.btn-stop:disabled {
  opacity: 0.35;
  cursor: not-allowed;
}

.btn-clear {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text-dim);
  padding: 6px 12px;
  font-family: var(--mono);
  font-size: 12px;
  border-radius: 4px;
  cursor: pointer;
}

.btn-clear:hover { color: var(--text); }

/* ---- Tweak panel (hyperparameter UI) ---- */

.tweak-panel {
  background: var(--panel);
  border-top: 1px solid var(--border);
}

.tweak-panel summary {
  list-style: none;
  cursor: pointer;
  padding: 10px 14px;
  font-family: var(--mono);
  font-size: 13px;
  color: var(--text);
  user-select: none;
  display: flex;
  align-items: center;
  gap: 6px;
}

.tweak-panel summary::-webkit-details-marker { display: none; }

.tweak-panel summary::before {
  content: "▸";
  color: var(--text-dim);
  display: inline-block;
  transition: transform 0.15s;
}

.tweak-panel[open] summary::before { transform: rotate(90deg); }

.tweak-icon { color: var(--accent); }

.tweak-hint { color: var(--text-dim); font-size: 12px; }

.tweak-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 16px;
  padding: 4px 14px 14px;
}

.tweak-demo h4 {
  font-family: var(--mono);
  font-size: 12px;
  color: var(--accent-2);
  margin: 0 0 8px;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.tweak-demo label {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 10px;
  margin-bottom: 6px;
  font-family: var(--mono);
  font-size: 12px;
  color: var(--text-dim);
}

.tweak-demo label span { flex: 1; }

.tweak-demo input[type="number"] {
  width: 100px;
  padding: 4px 8px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 4px;
  color: var(--text);
  font-family: var(--mono);
  font-size: 12px;
  text-align: right;
  -moz-appearance: textfield;
}

.tweak-demo input[type="number"]:focus {
  outline: none;
  border-color: var(--accent);
}

.tweak-demo input[type="number"]::-webkit-outer-spin-button,
.tweak-demo input[type="number"]::-webkit-inner-spin-button {
  opacity: 0.6;
}

.tweak-foot {
  margin: 0;
  padding: 0 14px 12px;
  font-family: var(--mono);
  font-size: 11px;
  color: var(--text-dim);
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 6px;
}

.btn-link {
  background: none;
  border: none;
  padding: 0;
  color: var(--accent);
  font-family: var(--mono);
  font-size: 11px;
  cursor: pointer;
  text-decoration: underline;
}

.btn-link:hover { color: var(--accent-2); }

.terminal {
  height: 460px;
  padding: 8px;
  background: var(--terminal-bg);
  overflow: hidden;
}

/* Force xterm's scrollbar to stay visible on macOS, which auto-hides native
 * scrollbars by default. Without this, users have no visual cue that the
 * terminal is scrollable. */
.terminal .xterm-viewport::-webkit-scrollbar { width: 10px; }
.terminal .xterm-viewport::-webkit-scrollbar-track { background: transparent; }
.terminal .xterm-viewport::-webkit-scrollbar-thumb {
  background: var(--border);
  border-radius: 5px;
}
.terminal .xterm-viewport::-webkit-scrollbar-thumb:hover {
  background: var(--text-dim);
}
.terminal .xterm-viewport {
  scrollbar-width: thin;
  scrollbar-color: var(--border) transparent;
}

.hint {
  font-family: var(--mono);
  font-size: 12px;
  color: var(--text);
  margin: 0;
  padding: 10px 14px;
  background: var(--panel);
  border-top: 1px solid var(--border);
}

.hint strong {
  color: var(--accent-2);
  font-weight: 600;
}

/* ---- How it works ---- */

.arch {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 20px;
  font-family: var(--mono);
  font-size: 13px;
  color: var(--text);
  overflow-x: auto;
  margin-bottom: 32px;
}

.arch pre {
  margin: 0;
  white-space: pre;
  color: var(--text);
}

.grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 14px;
}

@media (max-width: 640px) {
  .grid { grid-template-columns: 1fr; }
}

.card {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 18px 20px;
}

.card h3 {
  font-family: var(--mono);
  font-size: 14px;
  color: var(--accent-2);
  margin: 0 0 8px;
}

.card p {
  margin: 0;
  font-size: 14px;
  color: var(--text-dim);
}

.card strong { color: var(--text); font-weight: 600; }

/* ---- Tree ---- */

.tree {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 20px;
  font-family: var(--mono);
  font-size: 13px;
  line-height: 1.6;
  color: var(--text);
  overflow-x: auto;
  margin: 0 0 24px;
}

.cta { margin-top: 24px; }

/* ---- Footer ---- */

footer {
  padding: 32px 0;
  font-family: var(--mono);
  font-size: 13px;
  color: var(--text-dim);
  text-align: center;
}

/* ---- Mobile ---- */

@media (max-width: 640px) {
  .hero { padding: 56px 0 40px; }
  .hero h1 { font-size: 40px; }
  .tagline { font-size: 16px; }
  .stats { gap: 18px; }
  .stats li strong { font-size: 17px; }
  .section { padding: 48px 0; }
  .terminal { height: 380px; }
}