:root {
  --font-main: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-mono: 'DM Mono', monospace;

  /* Theme: Light */
  --bg-base: #f8fafc;
  --bg-canvas: #f1f5f9;
  --text-main: #0f172a;
  --text-bright: #020617;
  --text-dim: #64748b;
  --card-bg: rgba(255, 255, 255, 0.88);
  --card-border: rgba(226, 232, 240, 0.85);
  --card-hover: rgba(255, 255, 255, 0.98);
  --glass-border: rgba(148, 163, 184, 0.2);
  --glass: rgba(255, 255, 255, 0.65);

  --cyan: #0284c7;
  --cyan-dim: rgba(2, 132, 199, 0.12);
  --mint: #059669;
  --mint-dim: rgba(5, 150, 105, 0.12);
  --amber: #d97706;
  --amber-dim: rgba(217, 119, 6, 0.12);
  --purple: #7c3aed;
  --purple-dim: rgba(124, 58, 237, 0.12);
  --red: #dc2626;
  --red-dim: rgba(220, 38, 38, 0.12);

  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.04);
  --shadow-md: 0 8px 24px rgba(0, 0, 0, 0.08);
}

[data-theme="dark"] {
  --bg-base: #090d16;
  --bg-canvas: #040711;
  --text-main: #94a3b8;
  --text-bright: #f1f5f9;
  --text-dim: #64748b;
  --card-bg: rgba(15, 23, 42, 0.65);
  --card-border: rgba(255, 255, 255, 0.08);
  --card-hover: rgba(30, 41, 59, 0.85);
  --glass-border: rgba(255, 255, 255, 0.08);
  --glass: rgba(15, 23, 42, 0.4);

  --cyan: #38bdf8;
  --cyan-dim: rgba(56, 189, 248, 0.15);
  --mint: #34d399;
  --mint-dim: rgba(52, 211, 153, 0.15);
  --amber: #fbbf24;
  --amber-dim: rgba(251, 191, 36, 0.15);
  --purple: #c084fc;
  --purple-dim: rgba(192, 132, 252, 0.15);
  --red: #f87171;
  --red-dim: rgba(248, 113, 113, 0.15);

  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.4);
  --shadow-md: 0 8px 24px rgba(0, 0, 0, 0.5);
}

* { box-sizing: border-box; margin: 0; padding: 0; }
body {
  font-family: var(--font-main);
  background-color: var(--bg-base);
  color: var(--text-main);
  min-height: 100vh;
  line-height: 1.6;
  position: relative;
  overflow-x: hidden;
  transition: background-color 0.3s ease, color 0.3s ease;
}

.bg-canvas { position: fixed; top: 0; left: 0; right: 0; bottom: 0; z-index: 0; pointer-events: none; }
.orb { position: absolute; border-radius: 50%; filter: blur(120px); opacity: 0.25; }
.orb1 { width: 500px; height: 500px; background: #0284c7; top: -100px; left: -100px; }
.orb2 { width: 450px; height: 450px; background: #7c3aed; bottom: 10%; right: -50px; }
.orb3 { width: 400px; height: 400px; background: #059669; top: 40%; left: 30%; }

.grid-overlay {
  position: fixed; top: 0; left: 0; right: 0; bottom: 0;
  background-image: linear-gradient(var(--glass-border) 1px, transparent 1px), linear-gradient(90deg, var(--glass-border) 1px, transparent 1px);
  background-size: 40px 40px; opacity: 0.3; z-index: 0; pointer-events: none;
}

.main { position: relative; z-index: 1; max-width: 1200px; margin: 0 auto; padding: 2rem 1.5rem 5rem; }

/* Topbar */
.topbar { display: flex; justify-content: space-between; align-items: center; gap: 1rem; margin-bottom: 2rem; flex-wrap: wrap; }
.topbar-left { display: flex; gap: 0.6rem; align-items: center; flex-wrap: wrap; }
.ctrl-btn {
  display: inline-flex; align-items: center; gap: 0.5rem; padding: 0.55rem 1rem;
  background: var(--card-bg); border: 1px solid var(--card-border); border-radius: 12px;
  color: var(--text-bright); font-family: var(--font-mono); font-size: 0.8rem; font-weight: 500;
  text-decoration: none; cursor: pointer; backdrop-filter: blur(12px); box-shadow: var(--shadow-sm);
  transition: all 0.25s ease;
}
.ctrl-btn:hover { border-color: var(--cyan); color: var(--cyan); transform: translateY(-2px); }
.ctrl-btn.highlight { background: linear-gradient(135deg, var(--cyan-dim), var(--purple-dim)); border-color: var(--cyan); font-weight: 600; }
.ctrl-btn.highlight:hover { background: var(--cyan); color: #fff; }
.ctrl-btn svg { width: 16px; height: 16px; }

/* Hero */
.hero { margin-bottom: 2rem; }
.hero-org {
  display: inline-block; font-family: var(--font-mono); font-size: 0.8rem; font-weight: 600;
  color: var(--cyan); background: var(--cyan-dim); border: 1px solid rgba(2, 132, 199, 0.2);
  padding: 0.35rem 0.9rem; border-radius: 100px; margin-bottom: 0.8rem;
}
.hero-unit { font-family: var(--font-mono); font-size: 0.75rem; letter-spacing: 0.15em; text-transform: uppercase; color: var(--text-dim); margin-bottom: 0.5rem; }
.hero h1 { font-size: 2.6rem; font-weight: 900; color: var(--text-bright); line-height: 1.15; letter-spacing: -0.03em; margin-bottom: 0.6rem; }
.hero h1 .g { background: linear-gradient(135deg, var(--cyan), var(--purple)); -webkit-background-clip: text; -webkit-text-fill-color: transparent; }
.hero-sub { font-family: var(--font-mono); font-size: 0.9rem; color: var(--cyan); font-weight: 500; margin-bottom: 0.8rem; }
.hero-desc { max-width: 840px; font-size: 1rem; color: var(--text-dim); margin-bottom: 1.5rem; }

/* Method Selector Pills */
.method-pills {
  display: flex; gap: 0.6rem; flex-wrap: wrap; margin-bottom: 2rem;
  background: var(--card-bg); padding: 0.5rem; border-radius: 16px; border: 1px solid var(--card-border);
}
.m-pill-btn {
  padding: 0.75rem 1.2rem; background: transparent; border: none; border-radius: 12px;
  font-family: var(--font-mono); font-size: 0.82rem; font-weight: 600; color: var(--text-main);
  cursor: pointer; transition: all 0.2s ease;
}
.m-pill-btn:hover { color: var(--cyan); background: var(--glass); }
.m-pill-btn.active { background: var(--cyan); color: #fff; box-shadow: 0 4px 12px var(--cyan-dim); }

.method-content { display: none; }
.method-content.active { display: block; animation: fadeIn 0.3s ease; }

@keyframes fadeIn { from { opacity: 0; transform: translateY(10px); } to { opacity: 1; transform: translateY(0); } }

.guide-card {
  background: var(--card-bg); border: 1px solid var(--card-border); border-radius: 20px;
  padding: 2rem; backdrop-filter: blur(20px); box-shadow: var(--shadow-md);
}

.card-top-bar {
  border-bottom: 1px solid var(--glass-border); padding-bottom: 1.2rem; margin-bottom: 1.5rem;
}
.card-top-bar h2 { font-size: 1.45rem; font-weight: 800; color: var(--text-bright); margin-top: 0.3rem; }
.code-ref { font-family: var(--font-mono); font-size: 0.8rem; color: var(--cyan); margin-top: 0.2rem; }

.badge {
  display: inline-flex; align-items: center; padding: 0.25rem 0.65rem; border-radius: 100px;
  font-family: var(--font-mono); font-size: 0.68rem; font-weight: 700; text-transform: uppercase;
}
.badge-purple { background: var(--purple-dim); color: var(--purple); border: 1px solid rgba(124, 58, 237, 0.25); }
.badge-cyan { background: var(--cyan-dim); color: var(--cyan); border: 1px solid rgba(2, 132, 199, 0.25); }
.badge-amber { background: var(--amber-dim); color: var(--amber); border: 1px solid rgba(217, 119, 6, 0.25); }
.badge-mint { background: var(--mint-dim); color: var(--mint); border: 1px solid rgba(5, 150, 105, 0.25); }

/* Specs Grid */
.specs-grid {
  display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 0.8rem; margin-bottom: 1.8rem;
}
.spec-box {
  background: var(--glass); border: 1px solid var(--glass-border); border-radius: 12px;
  padding: 0.9rem; display: flex; flex-direction: column; gap: 0.25rem;
}
.spec-box .lbl { font-family: var(--font-mono); font-size: 0.7rem; text-transform: uppercase; color: var(--text-dim); }
.spec-box strong { font-size: 0.85rem; color: var(--text-bright); font-family: var(--font-mono); }

.section-divider {
  font-family: var(--font-mono); font-size: 0.75rem; font-weight: 800; letter-spacing: 0.12em;
  color: var(--cyan); margin: 1.5rem 0 1rem; border-left: 3px solid var(--cyan); padding-left: 0.6rem;
}

/* Accordion */
.step-accordion { display: flex; flex-direction: column; gap: 0.9rem; }
.acc-item {
  background: var(--glass); border: 1px solid var(--glass-border); border-radius: 14px; padding: 1.2rem;
}
.acc-title {
  font-family: var(--font-mono); font-size: 0.85rem; font-weight: 700; color: var(--text-bright);
  margin-bottom: 0.6rem; border-bottom: 1px solid var(--glass-border); padding-bottom: 0.4rem;
}
.acc-body { font-size: 0.9rem; line-height: 1.6; color: var(--text-main); }
.acc-body p { margin-bottom: 0.5rem; }

.table-wrap { overflow-x: auto; margin: 0.8rem 0; }
.method-table { width: 100%; border-collapse: collapse; font-size: 0.82rem; font-family: var(--font-mono); }
.method-table th { background: var(--glass); text-align: left; padding: 0.55rem 0.75rem; color: var(--text-dim); border-bottom: 1px solid var(--glass-border); }
.method-table td { padding: 0.5rem 0.75rem; border-bottom: 1px solid var(--glass-border); }

/* Cross-Linked Instruments */
.cross-link-container {
  background: var(--glass);
  border: 1.5px solid var(--glass-border);
  border-left: 4px solid var(--cyan);
  border-radius: 14px;
  padding: 1.1rem 1.2rem;
  margin: 1.4rem 0;
  backdrop-filter: blur(12px);
}
.cross-header {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.9rem;
  color: var(--text-bright);
  margin-bottom: 0.8rem;
  font-weight: 700;
}
.cross-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 0.75rem;
}
.inst-link-card {
  display: flex;
  flex-direction: column;
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: 10px;
  padding: 0.8rem 0.95rem;
  text-decoration: none;
  color: inherit;
  transition: all 0.2s ease;
  box-shadow: var(--shadow-sm);
}
.inst-link-card:hover {
  transform: translateY(-2px);
  border-color: var(--cyan);
  background: var(--card-hover);
  box-shadow: var(--shadow-md);
}
.inst-code {
  font-family: var(--font-mono);
  font-size: 0.65rem;
  font-weight: 700;
  color: var(--cyan);
}
.inst-name {
  font-size: 0.82rem;
  font-weight: 700;
  color: var(--text-bright);
  margin: 0.2rem 0 0.35rem;
  line-height: 1.3;
}
.inst-badge {
  font-family: var(--font-mono);
  font-size: 0.65rem;
  color: var(--mint);
  margin-top: auto;
  font-weight: 600;
}
.inst-link-card:hover .inst-badge {
  color: var(--cyan);
}

.footer {
  margin-top: 4rem; text-align: center; font-family: var(--font-mono); font-size: 0.8rem;
  color: var(--text-dim); padding: 2rem; border-top: 1px solid var(--glass-border);
}

/* Formula & Math Fraction Styles */
.formula-box {
  display: inline-flex; align-items: center; gap: 0.5rem; background: var(--glass);
  border: 1px solid var(--glass-border); border-radius: 8px; padding: 0.6rem 1rem;
  margin: 0.6rem 0; font-family: var(--font-mono); font-size: 0.88rem; color: var(--text-bright);
}
.math-fraction { display: inline-flex; flex-direction: column; vertical-align: middle; text-align: center; padding: 0 0.3rem; }
.fraction-top { border-bottom: 1.5px solid var(--text-bright); padding-bottom: 2px; }
.fraction-bot { padding-top: 2px; }