/* ===================== ScienceLab — Theme & Layout ===================== */
:root {
  --font: "Segoe UI", system-ui, -apple-system, Roboto, Helvetica, Arial, sans-serif;
  --radius: 14px;
  --radius-sm: 9px;
  --shadow: 0 6px 22px rgba(0,0,0,0.28);
  --maxw: 1240px;
  --phys: #4f8cff;
  --chem: #38c6a4;
  --bio: #ff8f5e;
  --transition: 160ms ease;
}

/* Dark theme (default) */
html[data-theme="dark"] {
  --bg: #0e1420;
  --bg-2: #141d2e;
  --surface: #1a2334;
  --surface-2: #212c40;
  --border: #2c3a52;
  --text: #e8eef7;
  --text-dim: #9fb0c8;
  --text-faint: #6f7f99;
  --accent: #5b9dff;
  --accent-contrast: #0e1420;
  --input-bg: #0f1826;
  --good: #46d18a;
  --warn: #ffb454;
  --bad: #ff6b6b;
  --grid-line: #24314a;
}

/* Light theme */
html[data-theme="light"] {
  --bg: #eef2f8;
  --bg-2: #e4ebf4;
  --surface: #ffffff;
  --surface-2: #f4f7fb;
  --border: #d3dced;
  --text: #16202f;
  --text-dim: #4a5a72;
  --text-faint: #7385a0;
  --accent: #2f6bd6;
  --accent-contrast: #ffffff;
  --input-bg: #ffffff;
  --good: #17a566;
  --warn: #c47a12;
  --bad: #d64545;
  --grid-line: #dbe3f0;
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  line-height: 1.5;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  transition: background var(--transition), color var(--transition);
}
a { color: var(--accent); text-decoration: none; }
h1, h2, h3, h4 { line-height: 1.2; margin: 0 0 .4em; }

/* ---------- Header ---------- */
.site-header {
  position: sticky; top: 0; z-index: 50;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
}
.header-inner {
  max-width: var(--maxw); margin: 0 auto; padding: 10px 20px;
  display: flex; align-items: center; gap: 18px;
}
.brand { display: flex; align-items: center; gap: 9px; font-weight: 700; font-size: 1.25rem; color: var(--text); }
.brand-mark { font-size: 1.4rem; }
.brand-accent { color: var(--accent); }
.top-nav { display: flex; align-items: center; gap: 6px; margin-left: 8px; }
.nav-link {
  background: none; border: none; cursor: pointer; font: inherit;
  color: var(--text-dim); padding: 8px 12px; border-radius: var(--radius-sm);
  transition: background var(--transition), color var(--transition);
}
.nav-link:hover, .nav-link.active { background: var(--surface); color: var(--text); }
.nav-group { position: relative; }
.nav-dropdown {
  position: absolute; top: calc(100% + 6px); left: 0; min-width: 260px;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  box-shadow: var(--shadow); padding: 8px; display: none; flex-direction: column; gap: 2px;
}
.nav-dropdown.open { display: flex; }
.nav-dropdown a {
  color: var(--text); padding: 8px 10px; border-radius: var(--radius-sm); font-size: .92rem;
  display: flex; align-items: center; gap: 9px;
}
.nav-dropdown a:hover { background: var(--surface-2); }
.nav-dot { width: 9px; height: 9px; border-radius: 50%; flex: none; }
.theme-toggle {
  margin-left: auto; background: var(--surface); border: 1px solid var(--border);
  color: var(--text); width: 42px; height: 42px; border-radius: 50%; cursor: pointer;
  font-size: 1.15rem; display: grid; place-items: center; transition: transform var(--transition), background var(--transition);
}
.theme-toggle:hover { transform: rotate(-12deg) scale(1.05); }

/* ---------- Main / Footer ---------- */
.app-main { flex: 1; max-width: var(--maxw); width: 100%; margin: 0 auto; padding: 26px 20px 48px; }
.site-footer { border-top: 1px solid var(--border); color: var(--text-faint); font-size: .82rem; text-align: center; padding: 18px 20px; }

/* ---------- Home / Hero ---------- */
.hero { text-align: center; padding: 22px 10px 30px; }
.hero h1 { font-size: clamp(1.8rem, 4vw, 2.7rem); margin-bottom: .3em; }
.hero p { color: var(--text-dim); max-width: 680px; margin: 0 auto; font-size: 1.05rem; }
.hero-tags { display: flex; gap: 8px; justify-content: center; flex-wrap: wrap; margin-top: 16px; }
.hero-tag { background: var(--surface); border: 1px solid var(--border); border-radius: 999px; padding: 5px 14px; font-size: .82rem; color: var(--text-dim); }

.subject-block { margin-top: 30px; }
.subject-head { display: flex; align-items: center; gap: 10px; margin-bottom: 14px; }
.subject-head .bar { width: 5px; height: 26px; border-radius: 3px; }
.subject-head h2 { margin: 0; font-size: 1.35rem; }
.subject-head .count { color: var(--text-faint); font-size: .85rem; margin-left: auto; }

.card-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 18px; }
.sim-card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 0; overflow: hidden; cursor: pointer; text-align: left; color: inherit;
  display: flex; flex-direction: column; transition: transform var(--transition), border-color var(--transition), box-shadow var(--transition);
}
.sim-card:hover { transform: translateY(-4px); box-shadow: var(--shadow); border-color: var(--accent); }
.sim-card .thumb { height: 118px; display: grid; place-items: center; font-size: 3rem; position: relative; }
.sim-card .thumb::after { content: ""; position: absolute; inset: 0; opacity: .16; }
.sim-card .body { padding: 15px 16px 18px; }
.sim-card h3 { font-size: 1.08rem; margin-bottom: 6px; }
.sim-card p { color: var(--text-dim); font-size: .9rem; margin: 0 0 10px; }
.sim-card .chips { display: flex; gap: 6px; flex-wrap: wrap; }
.chip { font-size: .72rem; padding: 3px 9px; border-radius: 999px; background: var(--surface-2); color: var(--text-dim); border: 1px solid var(--border); }

/* ---------- Sim page layout ---------- */
.sim-page { }
.breadcrumb { display: flex; align-items: center; gap: 8px; font-size: .85rem; color: var(--text-faint); margin-bottom: 8px; }
.breadcrumb a { color: var(--text-dim); }
.sim-title { display: flex; align-items: center; gap: 12px; flex-wrap: wrap; margin-bottom: 4px; }
.sim-title h1 { font-size: clamp(1.5rem, 3vw, 2rem); margin: 0; }
.subject-badge { font-size: .72rem; font-weight: 600; padding: 4px 11px; border-radius: 999px; color: #fff; }
.sim-intro { color: var(--text-dim); margin: 4px 0 18px; max-width: 820px; }

.tab-bar { display: flex; gap: 6px; border-bottom: 1px solid var(--border); margin-bottom: 18px; }
.tab-btn {
  background: none; border: none; border-bottom: 3px solid transparent; cursor: pointer; font: inherit;
  color: var(--text-dim); padding: 10px 16px; font-weight: 600; transition: color var(--transition), border-color var(--transition);
}
.tab-btn:hover { color: var(--text); }
.tab-btn.active { color: var(--accent); border-bottom-color: var(--accent); }
.tab-panel { display: none; }
.tab-panel.active { display: block; }

/* sim workspace: canvas + controls */
.sim-layout { display: grid; grid-template-columns: 1.5fr 1fr; gap: 20px; align-items: start; }
@media (max-width: 900px) { .sim-layout { grid-template-columns: 1fr; } }

.panel { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 16px; }
.panel h3 { font-size: 1rem; margin-bottom: 12px; color: var(--text); }
.stage-wrap { padding: 12px; }
canvas.sim-canvas { width: 100%; display: block; background: var(--bg-2); border-radius: var(--radius-sm); border: 1px solid var(--border); touch-action: none; }

.controls { display: flex; flex-direction: column; gap: 16px; }
.control { display: flex; flex-direction: column; gap: 6px; }
.control-row { display: flex; justify-content: space-between; align-items: baseline; }
.control label { font-weight: 600; font-size: .9rem; }
.control .val { font-variant-numeric: tabular-nums; color: var(--accent); font-weight: 700; }
input[type="range"] { -webkit-appearance: none; appearance: none; width: 100%; height: 6px; border-radius: 3px; background: var(--surface-2); outline: none; }
input[type="range"]::-webkit-slider-thumb { -webkit-appearance: none; width: 20px; height: 20px; border-radius: 50%; background: var(--accent); cursor: pointer; border: 3px solid var(--surface); box-shadow: 0 1px 4px rgba(0,0,0,.4); }
input[type="range"]::-moz-range-thumb { width: 18px; height: 18px; border-radius: 50%; background: var(--accent); cursor: pointer; border: 3px solid var(--surface); }
select, input[type="text"], input[type="number"] {
  background: var(--input-bg); color: var(--text); border: 1px solid var(--border);
  border-radius: var(--radius-sm); padding: 8px 10px; font: inherit; width: 100%;
}

.btn {
  background: var(--accent); color: var(--accent-contrast); border: none; border-radius: var(--radius-sm);
  padding: 9px 16px; font: inherit; font-weight: 600; cursor: pointer; transition: filter var(--transition), transform var(--transition);
}
.btn:hover { filter: brightness(1.08); }
.btn:active { transform: translateY(1px); }
.btn.secondary { background: var(--surface-2); color: var(--text); border: 1px solid var(--border); }
.btn.ghost { background: transparent; color: var(--text-dim); border: 1px solid var(--border); }
.btn-row { display: flex; gap: 10px; flex-wrap: wrap; }

/* readouts */
.readouts { display: grid; grid-template-columns: repeat(auto-fit, minmax(110px, 1fr)); gap: 10px; margin-top: 4px; }
.readout { background: var(--surface-2); border: 1px solid var(--border); border-radius: var(--radius-sm); padding: 10px 12px; }
.readout .k { font-size: .72rem; color: var(--text-faint); text-transform: uppercase; letter-spacing: .04em; }
.readout .v { font-size: 1.25rem; font-weight: 700; font-variant-numeric: tabular-nums; }
.readout .u { font-size: .8rem; color: var(--text-dim); font-weight: 400; }

.state-pill { display: inline-block; padding: 5px 14px; border-radius: 999px; font-weight: 700; font-size: .95rem; }

.note { background: var(--surface-2); border-left: 3px solid var(--accent); border-radius: 6px; padding: 10px 13px; font-size: .88rem; color: var(--text-dim); }
.note strong { color: var(--text); }

/* ---------- Worksheet ---------- */
.ws-toolbar { display: flex; align-items: center; gap: 12px; flex-wrap: wrap; margin-bottom: 16px; }
.level-switch { display: inline-flex; background: var(--surface-2); border: 1px solid var(--border); border-radius: 999px; padding: 3px; }
.level-switch button { background: none; border: none; cursor: pointer; font: inherit; font-weight: 600; color: var(--text-dim); padding: 7px 15px; border-radius: 999px; font-size: .85rem; }
.level-switch button.active { background: var(--accent); color: var(--accent-contrast); }
.ws-meta { display: grid; grid-template-columns: 1fr 1fr 1fr; gap: 12px; margin-bottom: 20px; }
@media (max-width: 640px) { .ws-meta { grid-template-columns: 1fr; } }
.ws-field label { font-size: .78rem; color: var(--text-faint); text-transform: uppercase; letter-spacing: .04em; display: block; margin-bottom: 4px; }

.ws-doc { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 24px; }
.ws-obj { background: var(--surface-2); border-radius: var(--radius-sm); padding: 14px 16px; margin-bottom: 20px; }
.ws-obj h4 { margin: 0 0 8px; font-size: .95rem; }
.ws-obj ul { margin: 0; padding-left: 20px; color: var(--text-dim); font-size: .9rem; }
.ws-level-label { font-size: .8rem; color: var(--text-faint); margin-bottom: 14px; }
.ws-q { margin-bottom: 20px; }
.ws-q .q-text { font-weight: 600; margin-bottom: 8px; display: flex; gap: 8px; }
.ws-q .q-num { color: var(--accent); font-weight: 700; flex: none; }
.ws-q .q-marks { color: var(--text-faint); font-weight: 400; font-size: .82rem; margin-left: auto; flex: none; }
.ws-q textarea, .ws-q input.ws-answer {
  width: 100%; background: var(--input-bg); color: var(--text); border: 1px solid var(--border);
  border-radius: var(--radius-sm); padding: 10px 12px; font: inherit; resize: vertical;
}
.ws-q textarea { min-height: 70px; }
.ws-hint { font-size: .82rem; color: var(--text-faint); margin-top: 5px; font-style: italic; }
.ws-saved { font-size: .8rem; color: var(--good); }

/* print header only shown when printing */
.print-only { display: none; }

/* ---------- Responsive nav ---------- */
@media (max-width: 620px) {
  .brand-text { display: none; }
  .nav-link[data-nav="home"] { display: none; }
}

/* ===================== PRINT ===================== */
@media print {
  @page { margin: 16mm; }
  body { background: #fff !important; color: #000 !important; display: block; }
  .site-header, .site-footer, .tab-bar, .sim-layout, .breadcrumb,
  .sim-title, .sim-intro, .ws-meta,
  .ws-toolbar, .theme-toggle, .no-print, .level-switch { display: none !important; }
  .app-main { max-width: none; margin: 0; padding: 0; }
  .print-only { display: block !important; }
  .ws-doc { border: none !important; padding: 0 !important; background: #fff !important; }
  .ws-obj { background: #f2f2f2 !important; border: 1px solid #ccc; }
  .ws-obj *, .ws-doc *, .print-only * { color: #000 !important; }
  .ws-q { break-inside: avoid; page-break-inside: avoid; margin-bottom: 16px; }
  .ws-q textarea, .ws-q input.ws-answer { border: 1px solid #888 !important; background: #fff !important; min-height: 60px; }
  .ws-q .q-num { color: #000 !important; }
  .print-head { border-bottom: 2px solid #000; padding-bottom: 8px; margin-bottom: 16px; }
  .print-head h1 { font-size: 18pt; margin: 0 0 4px; }
  .print-meta { display: flex; gap: 30px; font-size: 11pt; margin-top: 6px; }
  .print-meta div { border-bottom: 1px solid #000; min-width: 180px; padding-bottom: 2px; }
  .ws-hint { color: #444 !important; }
}