/* Shared look & feel for every lecture demo. No external fonts — works offline. */

:root {
  --bg: #f3f5f9;
  --panel: #ffffff;
  --panel-2: #f7f8fb;
  --ink: #18202f;
  --ink-2: #465063;
  --muted: #6f798d;
  --line: #e1e5ec;
  --line-strong: #c3cad6;
  --accent: #2f6bed;
  --accent-soft: #e7eefe;
  --on-strong: #ffffff;
  --good: #188a4c;
  --good-soft: #def5e7;
  --warn: #c27c00;
  --warn-soft: #fff1cc;
  --bad: #d93a40;
  --bad-soft: #fde6e6;
  --violet: #7445d4;
  --violet-soft: #eee6fd;
  --teal: #0b8a8f;
  --teal-soft: #d9f3f3;
  --orange: #dc6418;
  --orange-soft: #fdebdc;
  --key-bg: #edf1f8;
  --grid: rgba(24, 32, 47, 0.09);
  --node-shadow: rgba(16, 24, 40, 0.10);
  --shadow-sm: 0 1px 2px rgba(16, 24, 40, 0.06);
  --shadow: 0 1px 3px rgba(16, 24, 40, 0.06), 0 8px 24px rgba(16, 24, 40, 0.08);
  --radius: 10px;
  --font: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --mono: ui-monospace, "Cascadia Code", "SF Mono", Consolas, "Liberation Mono", monospace;
  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #0e1218;
    --panel: #171c25;
    --panel-2: #1d2330;
    --ink: #e8ecf3;
    --ink-2: #b6bfce;
    --muted: #8892a5;
    --line: #283041;
    --line-strong: #3b4559;
    --accent: #6b97ff;
    --accent-soft: #1c2a4b;
    --on-strong: #0e1218;
    --good: #46d18a;
    --good-soft: #143121;
    --warn: #f2b543;
    --warn-soft: #3a2c10;
    --bad: #ff6f73;
    --bad-soft: #3d1a1d;
    --violet: #ad8cff;
    --violet-soft: #2a2047;
    --teal: #45cfcf;
    --teal-soft: #113334;
    --orange: #ff9b52;
    --orange-soft: #3b2414;
    --key-bg: #242c3b;
    --grid: rgba(232, 236, 243, 0.08);
    --node-shadow: rgba(0, 0, 0, 0.35);
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
    --shadow: 0 1px 3px rgba(0, 0, 0, 0.3), 0 8px 24px rgba(0, 0, 0, 0.35);
    color-scheme: dark;
  }
}

:root[data-theme="dark"] {
  --bg: #0e1218;
  --panel: #171c25;
  --panel-2: #1d2330;
  --ink: #e8ecf3;
  --ink-2: #b6bfce;
  --muted: #8892a5;
  --line: #283041;
  --line-strong: #3b4559;
  --accent: #6b97ff;
  --accent-soft: #1c2a4b;
  --on-strong: #0e1218;
  --good: #46d18a;
  --good-soft: #143121;
  --warn: #f2b543;
  --warn-soft: #3a2c10;
  --bad: #ff6f73;
  --bad-soft: #3d1a1d;
  --violet: #ad8cff;
  --violet-soft: #2a2047;
  --teal: #45cfcf;
  --teal-soft: #113334;
  --orange: #ff9b52;
  --orange-soft: #3b2414;
  --key-bg: #242c3b;
  --grid: rgba(232, 236, 243, 0.08);
  --node-shadow: rgba(0, 0, 0, 0.35);
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
  --shadow: 0 1px 3px rgba(0, 0, 0, 0.3), 0 8px 24px rgba(0, 0, 0, 0.35);
  color-scheme: dark;
}

*,
*::before,
*::after { box-sizing: border-box; }

html,
body { margin: 0; }

body {
  background: var(--bg);
  color: var(--ink);
  font: 15px/1.45 var(--font);
  -webkit-font-smoothing: antialiased;
}

button,
input,
select { font: inherit; color: inherit; }

[hidden] { display: none !important; }

/* ---------- Icons (inline SVG sprite, see each page) ---------- */

.icon {
  width: 18px;
  height: 18px;
  flex: none;
  fill: none;
  stroke: currentColor;
  stroke-width: 2;
  stroke-linecap: round;
  stroke-linejoin: round;
}

/* ---------- Buttons & inputs ---------- */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  height: 36px;
  padding: 0 14px;
  border: 1px solid var(--line-strong);
  border-radius: 8px;
  background: var(--panel);
  font-size: 14px;
  font-weight: 600;
  white-space: nowrap;
  cursor: pointer;
  transition: background 0.15s, border-color 0.15s, color 0.15s;
}
.btn:hover { background: var(--panel-2); border-color: var(--muted); }
.btn:active { transform: translateY(1px); }
.btn:disabled { opacity: 0.4; cursor: not-allowed; transform: none; }
.btn:disabled:hover { background: var(--panel); border-color: var(--line-strong); }

.btn-primary { background: var(--accent); border-color: var(--accent); color: var(--on-strong); }
.btn-primary:hover { background: var(--accent); border-color: var(--accent); filter: brightness(0.93); }

.btn-danger { color: var(--bad); }
.btn-danger:hover { background: var(--bad-soft); border-color: var(--bad); }

.btn-icon { width: 36px; padding: 0; }
.btn-ghost { border-color: transparent; background: transparent; }
.btn-ghost:hover { background: var(--panel-2); border-color: var(--line); }
.btn.on { background: var(--accent-soft); border-color: var(--accent); color: var(--accent); }

.input {
  height: 36px;
  padding: 0 12px;
  border: 1px solid var(--line-strong);
  border-radius: 8px;
  background: var(--panel);
  min-width: 0;
}
.input::placeholder { color: var(--muted); }
select.input { padding-right: 8px; cursor: pointer; }

.btn:focus-visible,
.input:focus-visible,
select:focus-visible,
input[type="range"]:focus-visible,
a:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

.kbd {
  display: inline-block;
  min-width: 22px;
  padding: 1px 6px;
  border: 1px solid var(--line-strong);
  border-bottom-width: 2px;
  border-radius: 5px;
  background: var(--panel-2);
  font: 600 12px/1.5 var(--mono);
  text-align: center;
}

/* ---------- Segmented control ---------- */

.seg {
  display: inline-flex;
  padding: 2px;
  border: 1px solid var(--line-strong);
  border-radius: 8px;
  background: var(--panel-2);
}
.seg button {
  border: 0;
  border-radius: 6px;
  background: transparent;
  padding: 5px 12px;
  font-size: 13px;
  font-weight: 600;
  color: var(--ink-2);
  cursor: pointer;
}
.seg button.on { background: var(--panel); color: var(--accent); box-shadow: var(--shadow-sm); }
.seg.disabled { opacity: 0.45; pointer-events: none; }

/* ---------- Switch ---------- */

.switch { display: inline-flex; align-items: center; gap: 8px; cursor: pointer; font-size: 14px; font-weight: 600; user-select: none; }
.switch input { position: absolute; opacity: 0; pointer-events: none; }
.switch .track {
  position: relative;
  width: 36px;
  height: 20px;
  border-radius: 10px;
  background: var(--line-strong);
  transition: background 0.2s;
}
.switch .track::after {
  content: "";
  position: absolute;
  top: 2px;
  left: 2px;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: #fff;
  box-shadow: var(--shadow-sm);
  transition: transform 0.2s;
}
.switch input:checked + .track { background: var(--accent); }
.switch input:checked + .track::after { transform: translateX(16px); }
.switch input:focus-visible + .track { outline: 2px solid var(--accent); outline-offset: 2px; }

/* ---------- Theme toggle icon swap ---------- */

.theme-btn .i-sun { display: none; }
:root[data-theme="dark"] .theme-btn .i-sun { display: block; }
:root[data-theme="dark"] .theme-btn .i-moon { display: none; }
@media (prefers-color-scheme: dark) {
  :root:not([data-theme]) .theme-btn .i-sun { display: block; }
  :root:not([data-theme]) .theme-btn .i-moon { display: none; }
}

/* Author watermark (injected by shell.js on every page). */
.author-watermark {
  position: absolute;
  right: var(--watermark-right, 12px);
  bottom: var(--watermark-bottom, 12px);
  z-index: 5;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 5px 12px 5px 10px;
  border-radius: 999px;
  border: 1px solid var(--line);
  background: color-mix(in srgb, var(--panel) 70%, transparent);
  backdrop-filter: blur(6px);
  -webkit-backdrop-filter: blur(6px);
  box-shadow: var(--shadow-sm);
  font: 600 12px/1 var(--font);
  letter-spacing: 0.02em;
  color: var(--ink-2);
  opacity: 0.72;
  pointer-events: none;
  user-select: none;
}
.author-watermark .aw-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--accent), var(--violet));
}
.author-watermark .aw-by { font-weight: 400; color: var(--muted); }
.author-watermark .aw-name {
  background: linear-gradient(90deg, var(--accent), var(--violet));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
/* Pages without a drawing area pin it to the window instead. */
.author-watermark.fixed { position: fixed; z-index: 900; }
@media print { .author-watermark { opacity: 1; } }