/* ===========================================================================
   Astronomy Education — shared stylesheet
   Plain CSS, no build step. Dark "deep space" theme with light fallback.
   =========================================================================== */

:root {
  --bg: #0b1020;
  --bg-soft: #131a30;
  --panel: #182241;
  --panel-2: #1f2c52;
  --border: #2c3a66;
  --text: #e8ecf8;
  --text-dim: #9fabce;
  --accent: #6ea8fe;
  --accent-2: #b692ff;
  --accent-warm: #ffd166;
  --danger: #ff6b6b;
  --good: #4cd4a0;
  --shadow: 0 8px 30px rgba(0, 0, 0, 0.45);
  --radius: 14px;
  --maxw: 1180px;
  --font: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial,
    sans-serif;
  --mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: var(--font);
  color: var(--text);
  background:
    radial-gradient(1200px 600px at 80% -10%, rgba(110, 168, 254, 0.12), transparent 60%),
    radial-gradient(900px 500px at 0% 10%, rgba(182, 146, 255, 0.10), transparent 55%),
    var(--bg);
  background-attachment: fixed;
  line-height: 1.55;
  min-height: 100vh;
}

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

/* ---------- Layout ---------- */
.container { max-width: var(--maxw); margin: 0 auto; padding: 0 20px; }

.site-header {
  position: sticky; top: 0; z-index: 50;
  backdrop-filter: blur(10px);
  background: rgba(11, 16, 32, 0.78);
  border-bottom: 1px solid var(--border);
}
.site-header .bar {
  display: flex; align-items: center; gap: 16px;
  padding: 12px 20px; max-width: var(--maxw); margin: 0 auto;
}
.brand {
  display: flex; align-items: center; gap: 10px;
  font-weight: 700; font-size: 1.05rem; color: var(--text);
}
.brand:hover { text-decoration: none; }
.brand .logo {
  width: 30px; height: 30px; flex: 0 0 auto;
}
.spacer { flex: 1 1 auto; }

.site-nav { display: flex; gap: 6px; }
.site-nav a {
  color: var(--text-dim); font-size: 0.88rem; font-weight: 600;
  padding: 6px 12px; border-radius: 999px;
}
.site-nav a:hover { color: var(--text); background: var(--panel); text-decoration: none; }
@media (max-width: 560px) { .site-nav { display: none; } }

.lang-switch {
  display: inline-flex; border: 1px solid var(--border);
  border-radius: 999px; overflow: hidden; background: var(--panel);
}
.lang-switch button {
  border: 0; background: transparent; color: var(--text-dim);
  padding: 6px 12px; cursor: pointer; font-size: 0.82rem; font-weight: 600;
}
.lang-switch button.active { background: var(--accent); color: #06112b; }

/* ---------- Hero (home) ---------- */
.hero { padding: 54px 0 26px; text-align: center; }
.hero h1 {
  font-size: clamp(1.9rem, 4vw, 3rem); margin: 0 0 12px;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  -webkit-background-clip: text; background-clip: text; color: transparent;
}
.hero p { color: var(--text-dim); max-width: 720px; margin: 0 auto; font-size: 1.05rem; }
.hero .stat { color: var(--accent-warm); font-weight: 700; }

/* ---------- Controls row (search/filter) ---------- */
.toolbar {
  display: flex; flex-wrap: wrap; gap: 12px; align-items: center;
  margin: 24px 0 18px;
}
.search {
  flex: 1 1 260px; display: flex; align-items: center; gap: 8px;
  background: var(--panel); border: 1px solid var(--border);
  border-radius: 999px; padding: 8px 16px;
}
.search input {
  flex: 1; background: transparent; border: 0; color: var(--text);
  font-size: 0.95rem; outline: none;
}
.chips { display: flex; flex-wrap: wrap; gap: 8px; }
.chip {
  border: 1px solid var(--border); background: var(--panel);
  color: var(--text-dim); border-radius: 999px; padding: 6px 14px;
  cursor: pointer; font-size: 0.82rem; white-space: nowrap;
}
.chip.active { background: var(--accent); color: #06112b; border-color: var(--accent); font-weight: 600; }

/* ---------- Catalog ---------- */
.category-block { margin: 34px 0; }
.category-title {
  display: flex; align-items: baseline; gap: 12px;
  font-size: 1.35rem; margin: 0 0 4px;
}
.category-title .count { color: var(--text-dim); font-size: 0.9rem; font-weight: 400; }
.category-desc { color: var(--text-dim); margin: 0 0 16px; font-size: 0.95rem; }

.card-grid {
  display: grid; gap: 16px;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
}
.card {
  display: flex; flex-direction: column;
  background: linear-gradient(180deg, var(--panel), var(--bg-soft));
  border: 1px solid var(--border); border-radius: var(--radius);
  padding: 16px; position: relative; overflow: hidden;
  transition: transform 0.15s ease, border-color 0.15s ease, box-shadow 0.15s ease;
}
a.card { cursor: pointer; }
a.card:hover { transform: translateY(-3px); border-color: var(--accent); box-shadow: var(--shadow); }
.card .thumb {
  position: relative;
  height: 120px; border-radius: 10px; margin-bottom: 12px;
  background: radial-gradient(120px 80px at 70% 20%, rgba(110,168,254,.25), transparent),
              var(--bg); border: 1px solid var(--border);
  display: flex; align-items: center; justify-content: center; overflow: hidden;
}
.card .thumb svg { width: 100%; height: 100%; }
.card .thumb img {
  position: absolute; inset: 0; width: 100%; height: 100%;
  object-fit: cover; display: block; background: #05070f;
}
.card h3 { margin: 0 0 6px; font-size: 1.02rem; }
.card p { margin: 0; color: var(--text-dim); font-size: 0.88rem; flex: 1; }

.card.compact { padding-top: 16px; }
.card.compact h3 { font-size: 0.96rem; }
.card.compact p { font-size: 0.84rem; }
a.chip { text-decoration: none; }
a.chip:hover { text-decoration: none; color: var(--text); border-color: var(--accent); }

.card-actions { margin-top: 12px; display: flex; gap: 8px; flex-wrap: wrap; }
.mini-btn {
  display: inline-flex; align-items: center; gap: 5px;
  font-size: 0.8rem; font-weight: 600; padding: 6px 11px; border-radius: 8px;
  border: 1px solid var(--border); background: var(--panel-2); color: var(--text);
  cursor: pointer; white-space: nowrap;
}
.mini-btn:hover { border-color: var(--accent); text-decoration: none; }
.mini-btn.primary { background: var(--accent); color: #06112b; border-color: var(--accent); }
.mini-btn.flash { color: var(--accent-2); }
.mini-btn.flash:hover { border-color: var(--accent-2); }

/* Ruffle player stage */
.play-stage {
  margin: 8px 0 4px; background: #05070f; border: 1px solid var(--border);
  border-radius: var(--radius); box-shadow: var(--shadow);
  height: min(72vh, 640px); min-height: 420px;
  display: flex; align-items: center; justify-content: center;
  overflow: hidden;
}
.play-stage ruffle-player, .play-stage > * { width: 100%; height: 100%; }
.play-stage { position: relative; }
.play-stage > .play-paused {
  position: absolute; top: 10px; right: 12px; width: auto; height: auto;
  padding: 5px 11px; border-radius: 999px; font-size: 12px; line-height: 1.3;
  background: rgba(11, 16, 32, 0.84); color: var(--text-dim);
  border: 1px solid var(--border); pointer-events: none;
}
.play-stage > .play-paused[hidden] { display: none; }
.play-msg { color: var(--text-dim); padding: 40px; text-align: center; }
.play-msg.err { color: var(--danger); }
.play-msg a { color: var(--accent); }

.empty { text-align: center; color: var(--text-dim); padding: 60px 0; }

/* ---------- Footer ---------- */
.site-footer {
  border-top: 1px solid var(--border); margin-top: 60px;
  padding: 28px 0; color: var(--text-dim); font-size: 0.86rem;
}
.site-footer .container { display: flex; flex-wrap: wrap; gap: 10px 24px; justify-content: space-between; }
.footer-links { display: inline-flex; flex-wrap: wrap; align-items: center; gap: 6px 12px; }
.footer-links a { color: var(--text-dim); text-decoration: none; }
.footer-links a:hover, .footer-links a:focus-visible { color: var(--accent); text-decoration: underline; }
.footer-links .gh-link { display: inline-flex; align-items: center; gap: 6px; }
.footer-links .gh-icon { flex: none; }
.footer-links .sep { opacity: 0.5; }

/* ===========================================================================
   Simulation page
   =========================================================================== */
.breadcrumb { color: var(--text-dim); font-size: 0.85rem; padding: 16px 0 0; }
.breadcrumb a { color: var(--text-dim); }

.sim-head { padding: 8px 0 18px; }
.sim-head h1 { margin: 6px 0 8px; font-size: clamp(1.5rem, 3vw, 2.1rem); }
.sim-head p { margin: 0; color: var(--text-dim); max-width: 860px; }

.sim-layout {
  display: grid; gap: 20px;
  grid-template-columns: minmax(0, 1fr) 320px;
  align-items: start;
}
@media (max-width: 880px) { .sim-layout { grid-template-columns: 1fr; } }

.sim-stage {
  background: #05070f; border: 1px solid var(--border);
  border-radius: var(--radius); padding: 10px; box-shadow: var(--shadow);
}
.sim-stage canvas { width: 100%; height: auto; display: block; border-radius: 8px; }

.sim-controls {
  background: var(--panel); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 18px; display: flex; flex-direction: column; gap: 16px;
}
.sim-controls .group-title {
  font-size: 0.74rem; text-transform: uppercase; letter-spacing: .06em;
  color: var(--accent); font-weight: 700; margin: 4px 0 -4px;
}

.ctl { display: flex; flex-direction: column; gap: 6px; }
.ctl label { font-size: 0.86rem; color: var(--text); display: flex; justify-content: space-between; gap: 10px; }
.ctl label .val { color: var(--accent-warm); font-variant-numeric: tabular-nums; font-family: var(--mono); font-size: .82rem; }
.ctl input[type="range"] { width: 100%; accent-color: var(--accent); }
/* labels under a slider, each placed along the track by its own left: calc() */
.slider-scale { position: relative; height: 22px; margin-top: -2px; }
.slider-scale button {
  position: absolute; top: 0; transform: translateX(-50%);
  background: none; border: 0; padding: 0 3px; cursor: pointer;
  font-family: inherit; font-size: 0.95rem; font-weight: 800; line-height: 1.3;
  text-shadow: 0 0 1px rgba(0, 0, 0, 0.9);
}
.slider-scale button:hover, .slider-scale button:focus-visible { text-decoration: underline; }
.ctl select, .ctl input[type="number"] {
  background: var(--bg); border: 1px solid var(--border); color: var(--text);
  border-radius: 8px; padding: 7px 10px; font-size: 0.9rem;
}
.ctl.row { flex-direction: row; align-items: center; gap: 10px; }
.ctl.row label { justify-content: flex-start; }

/* small explanatory line inside the controls column */
.sim-note { margin: -2px 0 2px; font-size: 0.76rem; line-height: 1.5; color: var(--text-dim); font-style: italic; }

.btn {
  border: 1px solid var(--border); background: var(--panel-2); color: var(--text);
  border-radius: 9px; padding: 9px 14px; cursor: pointer; font-size: 0.9rem; font-weight: 600;
}
.btn:hover { border-color: var(--accent); }
.btn.primary { background: var(--accent); color: #06112b; border-color: var(--accent); }
.btn-row { display: flex; gap: 10px; flex-wrap: wrap; }

.readouts { display: grid; grid-template-columns: 1fr 1fr; gap: 8px 14px; }
.readout { background: var(--bg); border: 1px solid var(--border); border-radius: 8px; padding: 8px 10px; }
.readout .k { font-size: 0.7rem; color: var(--text-dim); text-transform: uppercase; letter-spacing: .04em; }
.readout .v { font-family: var(--mono); font-size: 0.98rem; color: var(--accent-warm); }

.sim-explain {
  margin-top: 26px; background: var(--bg-soft); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 22px 26px;
}
.sim-explain h2 { margin-top: 0; font-size: 1.2rem; }
.sim-explain h3 { font-size: 1rem; color: var(--accent); margin: 18px 0 6px; }
.sim-explain p, .sim-explain li { color: var(--text-dim); }
.sim-explain ul { padding-left: 20px; }

.toggle { display: inline-flex; align-items: center; gap: 8px; cursor: pointer; font-size: 0.88rem; }
.toggle input { width: 16px; height: 16px; accent-color: var(--accent); }

.visually-hidden { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); }