/* styles.css — Long-form, single-column build-it-up explainer. Warm colourful
   theme (Baloo 2 / Nunito), calm narrow reading column, vivid figures. */

:root {
  --bg: #fff7ef;
  --bg-2: #ffeede;
  --ink: #241b3a;
  --ink-soft: #5b5170;
  --paper: #ffffff;
  --line: #efe2d4;

  --red: #ff4757;
  --green: #2ed573;
  --blue: #1e90ff;
  --yellow: #ffc312;
  --orange: #ff9f1c;
  --purple: #7b5cff;
  --accent: var(--blue);

  --col: 680px;
  --fig: 760px;
  --radius: 20px;
  --shadow: 0 14px 40px rgba(60, 40, 90, 0.10);
  --sans: 'Nunito', 'Noto Sans SC', system-ui, sans-serif;
  --display: 'Baloo 2', 'Noto Sans SC', system-ui, sans-serif;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  color: var(--ink);
  font-family: var(--sans);
  font-size: 19px;
  line-height: 1.62;
  background:
    radial-gradient(1200px 700px at 80% -10%, var(--bg-2), transparent 60%),
    radial-gradient(900px 600px at -10% 110%, #eef3ff, transparent 55%),
    var(--bg);
  -webkit-font-smoothing: antialiased;
}
:lang(zh) body { font-family: 'Noto Sans SC', var(--sans); }

/* ---- top bar ---- */
.bar {
  display: flex; align-items: center; justify-content: space-between;
  max-width: var(--fig); margin: 0 auto; padding: 22px 24px 0;
}
.bar .home {
  display: inline-flex; align-items: center; gap: 10px;
  font-family: var(--display); font-weight: 800; color: var(--ink);
  text-decoration: none; font-size: 1.1rem;
}
.bar .home::before {
  content: ''; width: 22px; height: 22px; border-radius: 50%;
  background: conic-gradient(from 20deg, var(--orange), var(--yellow), var(--green), var(--blue), var(--purple), var(--orange));
  box-shadow: inset 0 0 0 5px #fff, inset 0 0 0 7px var(--ink);
}
.lang-toggle {
  font-family: var(--display); font-weight: 700; font-size: 0.9rem;
  border: 2px solid var(--ink); background: var(--ink); color: #fff;
  border-radius: 999px; padding: 6px 16px; cursor: pointer; transition: transform .15s, background .2s;
}
.lang-toggle:hover { transform: translateY(-1px); background: var(--purple); border-color: var(--purple); }

/* ---- article ---- */
article { max-width: var(--fig); margin: 0 auto; padding: 0 24px 14vh; }

h1 {
  font-family: var(--display); font-weight: 800; letter-spacing: -.01em;
  font-size: clamp(2.2rem, 4.6vw, 3rem); line-height: 1.08;
  margin: 0.7em auto 0.12em; max-width: var(--col);
}
.lede { max-width: var(--col); margin: 0.5em auto 0; color: var(--ink-soft); font-size: 1.18rem; }

h2 {
  font-family: var(--display); font-weight: 800; letter-spacing: -.005em;
  font-size: clamp(1.5rem, 3vw, 1.9rem); line-height: 1.16; color: var(--ink);
  max-width: var(--col); margin: 2.3em auto 0.3em;
}
p { max-width: var(--col); margin: 0.9em auto; }
a { color: var(--accent); text-decoration: none; font-weight: 700; }
a:hover { text-decoration: underline; }

/* ---- figures ---- */
figure { margin: 1.8em auto; max-width: var(--fig); }
.stage {
  width: 100%; height: min(58vw, 440px);
  background: radial-gradient(120% 120% at 50% 0%, #ffffff, var(--bg-2) 90%);
  border: 1px solid var(--line); border-radius: 24px; overflow: hidden;
  box-shadow: var(--shadow);
}
.stage canvas { width: 100%; height: 100%; display: block; cursor: grab; touch-action: pan-y; }
.stage canvas:active { cursor: grabbing; }

figcaption { max-width: var(--col); margin: 0.7em auto 0; color: var(--ink-soft); font-size: 0.95rem; text-align: center; }
.figdesc { max-width: var(--col); margin: 0 auto 0.6em; color: var(--ink-soft); }

/* exploded-view colour legend */
.legend { display: flex; flex-wrap: wrap; justify-content: center; gap: 8px 18px; max-width: var(--col); margin: 0 auto 0.7em; }
.legend-item { display: inline-flex; align-items: center; gap: 7px; font-size: 0.9rem; color: var(--ink); font-weight: 600; }
.sw { width: 14px; height: 14px; border-radius: 4px; display: inline-block; border: 1px solid rgba(0,0,0,.12); }
.sw-in { background: #ff9f1c; }
.sw-disc { background: #1e90ff; }
.sw-out { background: #2ed573; }

/* counters + slider in captions */
.fig-readout { font-family: var(--display); font-weight: 700; font-variant-numeric: tabular-nums; color: var(--ink); }
.fig-readout b { color: var(--accent); font-weight: 800; }
.fig-controls { display: flex; align-items: center; justify-content: center; gap: 14px; flex-wrap: wrap; max-width: var(--col); margin: 0.7em auto 0.3em; }
.fig-slider {
  -webkit-appearance: none; appearance: none; width: 220px; height: 6px;
  border-radius: 999px; background: var(--bg-2); border: 1px solid var(--line); cursor: pointer; vertical-align: middle;
}
.fig-slider::-webkit-slider-thumb { -webkit-appearance: none; appearance: none; width: 22px; height: 22px; border-radius: 50%; background: var(--blue); border: 3px solid #fff; box-shadow: 0 2px 6px rgba(30,40,90,.3); }
.fig-slider::-moz-range-thumb { width: 22px; height: 22px; border-radius: 50%; background: var(--blue); border: 3px solid #fff; }
.fig-controls .tag { font-family: var(--display); font-weight: 700; font-size: 1rem; color: var(--ink-soft); font-variant-numeric: tabular-nums; }
.fig-controls .tag b { color: var(--ink); font-weight: 800; }

/* ---- WebGL fallback ---- */
.webgl-banner { display: none; }
body.no-webgl .webgl-banner {
  display: block; max-width: var(--col); margin: 1.5em auto; padding: 14px 18px;
  background: var(--paper); border: 1px solid var(--line); border-radius: var(--radius); color: var(--ink-soft); text-align: center;
}
body.no-webgl .stage { display: none; }

@media (max-width: 720px) {
  body { font-size: 17px; }
  .stage { height: 72vw; }
}
@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } }