/* === Calculus for Computer Science — interactive toolkit === */

:root {
  --bg: #0a0e1a;
  --bg-2: #0f1424;
  --card: #131826;
  --card-2: #19203a;
  --border: #232c47;
  --border-soft: #1a2238;
  --text: #e8ecf4;
  --muted: #8a93a8;
  --dim: #5a627a;
  --primary: #5aa9ff;
  --primary-dim: #2f6fc7;
  --rose: #ff7eb3;
  --teal: #6ee7b7;
  --gold: #f7c873;
  --danger: #ff6e6e;
  --mono: 'JetBrains Mono', ui-monospace, 'SF Mono', Menlo, Consolas, monospace;
  --ui: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--ui);
  font-size: 15px;
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
  display: flex;
  min-height: 100vh;
}

a { color: var(--primary); text-decoration: none; }
a:hover { color: #8cc4ff; }
code, kbd, pre { font-family: var(--mono); }
kbd {
  background: var(--card-2);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 1px 6px;
  font-size: 12px;
}

/* ===================== SIDEBAR ===================== */
.sidebar {
  width: 260px;
  flex-shrink: 0;
  background: var(--bg-2);
  border-right: 1px solid var(--border-soft);
  padding: 22px 0 30px;
  position: sticky;
  top: 0;
  height: 100vh;
  overflow-y: auto;
  z-index: 50;
}
.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 0 22px 18px;
  border-bottom: 1px solid var(--border-soft);
  margin-bottom: 14px;
}
.brand-mark {
  font-size: 32px;
  font-weight: 600;
  color: var(--primary);
  width: 42px;
  height: 42px;
  display: grid;
  place-items: center;
  background: linear-gradient(135deg, #1a2950, #0e1730);
  border-radius: 10px;
  border: 1px solid var(--border);
  font-family: 'Cambria', 'Times New Roman', serif;
}
.brand-title {
  font-weight: 600;
  font-size: 14px;
  line-height: 1.15;
}
.brand-sub {
  color: var(--muted);
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-top: 2px;
}
.nav-list { list-style: none; margin: 0; padding: 0 12px; }
.nav-group {
  color: var(--dim);
  font-size: 10.5px;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  padding: 18px 10px 6px;
  font-weight: 600;
}
.nav-link {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 8px 10px;
  border-radius: 7px;
  color: var(--text);
  font-size: 13.5px;
  font-weight: 450;
}
.nav-link:hover { background: var(--card); }
.nav-link.active {
  background: linear-gradient(90deg, rgba(90,169,255,0.18), rgba(90,169,255,0.04));
  color: #cfe2ff;
  border-left: 2px solid var(--primary);
  padding-left: 8px;
}
.nav-code {
  font-family: var(--mono);
  font-size: 10.5px;
  color: var(--muted);
  background: var(--card);
  border-radius: 4px;
  padding: 2px 6px;
  min-width: 44px;
  text-align: center;
  border: 1px solid var(--border-soft);
}
.nav-link.active .nav-code { color: var(--primary); border-color: var(--primary-dim); }
.sidebar-foot {
  padding: 22px 22px 0;
  font-size: 12px;
  color: var(--muted);
}

/* ===================== MAIN ===================== */
.main {
  flex: 1;
  min-width: 0;
  padding: 40px 48px 80px;
  max-width: 1400px;
}

.module { display: none; }
.module.active { display: block; animation: fade 0.25s ease-out; }
@keyframes fade {
  from { opacity: 0; transform: translateY(6px); }
  to { opacity: 1; transform: translateY(0); }
}

/* ===================== HERO ===================== */
.hero {
  padding: 28px 0 40px;
  border-bottom: 1px solid var(--border-soft);
  margin-bottom: 36px;
}
.hero-eyebrow {
  color: var(--rose);
  font-size: 11.5px;
  text-transform: uppercase;
  letter-spacing: 0.14em;
  font-weight: 600;
  margin-bottom: 14px;
}
.hero-title {
  font-size: 54px;
  font-weight: 700;
  line-height: 1.05;
  letter-spacing: -0.02em;
  margin: 0 0 18px;
  background: linear-gradient(135deg, #e8ecf4 0%, #8cc4ff 70%);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}
.hero-accent { color: var(--rose); -webkit-text-fill-color: var(--rose); }
.hero-sub {
  font-size: 17px;
  color: var(--muted);
  max-width: 720px;
  line-height: 1.55;
}
.hero-stats {
  display: flex;
  gap: 48px;
  margin-top: 28px;
}
.hero-stats > div { display: flex; flex-direction: column; gap: 2px; }
.stat-num {
  font-size: 28px;
  font-weight: 700;
  color: var(--primary);
  font-family: var(--mono);
}
.stat-label {
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--muted);
}

/* ===================== CARDS ===================== */
.card {
  background: var(--card);
  border: 1px solid var(--border-soft);
  border-radius: 12px;
  padding: 24px 28px;
  margin: 0 0 22px;
}
.card h2 {
  font-size: 18px;
  font-weight: 600;
  margin: 0 0 12px;
  color: #cfe2ff;
}
.card h3 {
  font-size: 14px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--muted);
  margin: 20px 0 10px;
}
.card p, .card li { color: #c8cee0; font-size: 14.5px; }
.muted { color: var(--muted) !important; font-size: 13px; }
.card code, .examples code, .syntax code {
  background: var(--card-2);
  border: 1px solid var(--border-soft);
  padding: 1.5px 6px;
  border-radius: 4px;
  font-size: 12.5px;
  color: var(--gold);
}

/* ===================== MODULE CARD GRID ===================== */
.grid-modules {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 14px;
  margin: 0 0 22px;
}
.mod-card {
  background: var(--card);
  border: 1px solid var(--border-soft);
  border-radius: 11px;
  padding: 16px;
  display: flex;
  flex-direction: column;
  gap: 6px;
  color: var(--text);
  transition: transform 0.15s ease, border-color 0.15s ease, background 0.15s ease;
}
.mod-card:hover {
  transform: translateY(-2px);
  border-color: var(--primary-dim);
  background: #161d36;
}
.mod-code {
  font-family: var(--mono);
  font-size: 10.5px;
  color: var(--primary);
  letter-spacing: 0.05em;
  width: fit-content;
  background: rgba(90,169,255,0.1);
  padding: 2px 7px;
  border-radius: 4px;
}
.mod-name { font-weight: 600; font-size: 15px; color: var(--text); }
.mod-desc { color: var(--muted); font-size: 13px; line-height: 1.45; }

/* ===================== MODULE PAGE ===================== */
.mod-head {
  margin-bottom: 24px;
  padding-bottom: 18px;
  border-bottom: 1px solid var(--border-soft);
}
.mod-badge {
  display: inline-block;
  font-family: var(--mono);
  font-size: 11.5px;
  color: var(--primary);
  background: rgba(90,169,255,0.1);
  border: 1px solid rgba(90,169,255,0.3);
  padding: 3px 10px;
  border-radius: 5px;
  letter-spacing: 0.06em;
  margin-bottom: 12px;
}
.mod-head h2 {
  font-size: 30px;
  font-weight: 700;
  margin: 0 0 8px;
  letter-spacing: -0.01em;
}
.mod-tagline {
  color: var(--muted);
  font-size: 15px;
  margin: 0;
  max-width: 740px;
}

/* ===================== MOD GRID ===================== */
.mod-grid {
  display: grid;
  grid-template-columns: minmax(280px, 360px) 1fr;
  gap: 22px;
  align-items: stretch;
}
@media (max-width: 1000px) {
  .mod-grid { grid-template-columns: 1fr; }
}

.panel {
  background: var(--card);
  border: 1px solid var(--border-soft);
  border-radius: 12px;
  padding: 20px;
  display: flex;
  flex-direction: column;
  gap: 12px;
}
.panel label {
  display: flex;
  flex-direction: column;
  gap: 4px;
  font-size: 12px;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  font-weight: 600;
}
.panel input[type=text],
.panel input[type=number],
.panel select {
  background: var(--bg);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 9px 11px;
  border-radius: 7px;
  font-family: var(--mono);
  font-size: 14px;
  outline: none;
  transition: border-color 0.15s;
}
.panel input:focus, .panel select:focus { border-color: var(--primary); }
.panel input[type=range] {
  -webkit-appearance: none;
  appearance: none;
  width: 100%;
  background: transparent;
  margin: 4px 0;
}
.panel input[type=range]::-webkit-slider-runnable-track {
  height: 4px;
  background: var(--border);
  border-radius: 4px;
}
.panel input[type=range]::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  height: 16px;
  width: 16px;
  background: var(--primary);
  border-radius: 50%;
  margin-top: -6px;
  cursor: pointer;
  border: 3px solid var(--bg);
}
.panel input[type=range]::-moz-range-track { height: 4px; background: var(--border); border-radius: 4px; }
.panel input[type=range]::-moz-range-thumb { height: 16px; width: 16px; background: var(--primary); border-radius: 50%; border: 3px solid var(--bg); cursor: pointer; }

.btn {
  background: var(--primary);
  color: #08111e;
  border: none;
  padding: 11px 18px;
  border-radius: 7px;
  font-family: var(--ui);
  font-weight: 600;
  font-size: 13.5px;
  cursor: pointer;
  letter-spacing: 0.02em;
  transition: background 0.15s;
}
.btn:hover { background: #7ab8ff; }
.btn:active { transform: translateY(1px); }

.result {
  background: var(--bg);
  border: 1px solid var(--border-soft);
  border-radius: 8px;
  padding: 14px;
  font-family: var(--mono);
  font-size: 12.5px;
  color: var(--text);
  white-space: pre-wrap;
  min-height: 60px;
  word-break: break-word;
}
.result .label { color: var(--muted); }
.result .val { color: var(--gold); }
.result .verdict {
  display: inline-block;
  margin-top: 8px;
  padding: 5px 12px;
  border-radius: 5px;
  font-weight: 600;
  font-size: 12px;
  letter-spacing: 0.05em;
  text-transform: uppercase;
}
.result .verdict.good { background: rgba(110,231,183,0.15); color: var(--teal); border: 1px solid rgba(110,231,183,0.3); }
.result .verdict.bad { background: rgba(255,110,110,0.15); color: var(--danger); border: 1px solid rgba(255,110,110,0.3); }
.result .verdict.warn { background: rgba(247,200,115,0.15); color: var(--gold); border: 1px solid rgba(247,200,115,0.3); }
.result .verdict.info { background: rgba(90,169,255,0.15); color: var(--primary); border: 1px solid rgba(90,169,255,0.3); }
.result .err { color: var(--danger); }
.result table { width: 100%; font-size: 12px; border-collapse: collapse; }
.result table td { padding: 3px 8px 3px 0; }
.result table td:last-child { color: var(--gold); text-align: right; }

.plot, .plot-stack > .plot {
  background: var(--card);
  border: 1px solid var(--border-soft);
  border-radius: 12px;
  min-height: 460px;
  padding: 10px;
}
.plot-stack {
  display: flex;
  flex-direction: column;
  gap: 18px;
}
.plot-stack > .plot { min-height: 360px; }

/* TI-BASIC source block */
.src { margin-top: 4px; }
.src summary {
  cursor: pointer;
  color: var(--muted);
  font-size: 12.5px;
  user-select: none;
  padding: 6px 0;
}
.src summary:hover { color: var(--primary); }
.src pre {
  background: var(--bg);
  border: 1px solid var(--border-soft);
  border-radius: 8px;
  padding: 14px;
  font-size: 11.5px;
  line-height: 1.55;
  color: #b6c0d8;
  overflow-x: auto;
  margin: 8px 0 0;
}

/* Syntax page */
.syntax {
  width: 100%;
  border-collapse: collapse;
  font-size: 14px;
  margin: 8px 0 20px;
}
.syntax th, .syntax td {
  text-align: left;
  padding: 8px 14px 8px 0;
  border-bottom: 1px solid var(--border-soft);
}
.syntax th { color: var(--muted); font-weight: 600; font-size: 11.5px; text-transform: uppercase; letter-spacing: 0.08em; }
.examples { padding-left: 18px; }
.examples li { padding: 4px 0; color: #c8cee0; }

/* Footer */
.footer {
  margin-top: 60px;
  padding-top: 24px;
  border-top: 1px solid var(--border-soft);
  color: var(--muted);
  font-size: 13px;
}
.footer p { margin: 4px 0; }

/* Menu toggle (mobile) */
.menu-toggle {
  display: none;
  position: fixed;
  top: 14px;
  right: 14px;
  z-index: 100;
  background: var(--card);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 8px;
  width: 42px;
  height: 42px;
  font-size: 20px;
  cursor: pointer;
}

@media (max-width: 800px) {
  .sidebar {
    position: fixed;
    left: -280px;
    transition: left 0.25s ease;
  }
  .sidebar.open { left: 0; }
  .main { padding: 60px 20px 60px; }
  .menu-toggle { display: block; }
  .hero-title { font-size: 36px; }
  .hero-stats { gap: 22px; }
}

/* MathJax tweaks */
mjx-container { color: inherit; }
.mod-tagline mjx-container { color: var(--muted) !important; }