/* =========================================
   1. CORE VARIABLES & RESET
   ========================================= */
:root {
  --bg-1: #060617;
  --bg-2: #0b1020;
  --accent: #59f0ff;
  --muted: rgba(255,255,255,0.65);
  --glass: rgba(255, 255, 255, 0.03);
  --glass-border: rgba(255, 255, 255, 0.05);
}

* {
  box-sizing: border-box;
}

html, body {
  height: 100%;
  margin: 0;
  font-family: 'Inter', system-ui, -apple-system, sans-serif;
  background: var(--bg-1);
  color: #e8f6ff;
  line-height: 1.6;
}

.container {
  max-width: 1000px;
  margin: 0 auto;
  padding: 24px;
}

/* =========================================
   2. DYNAMIC BACKGROUND
   ========================================= */
.canvas-bg {
  position: fixed;
  inset: 0;
  z-index: -2;
  pointer-events: none;
  background: 
    radial-gradient(ellipse at 20% 10%, rgba(74,19,255,0.18), transparent 15%),
    radial-gradient(ellipse at 80% 80%, rgba(10,200,255,0.08), transparent 20%),
    linear-gradient(120deg, #030316 0%, #071029 50%, #04102a 100%);
  animation: bgShift 20s linear infinite;
}

.canvas-bg::after {
  content: '';
  position: absolute;
  inset: 0;
  mix-blend-mode: screen;
  opacity: 0.12;
  background-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" width="200" height="200"><filter id="n"><feTurbulence baseFrequency="0.8" numOctaves="1" stitchTiles="stitch"/></filter><rect width="100%" height="100%" filter="url(%23n)" opacity="0.8"/></svg>');
}

@keyframes bgShift {
  from { transform: scale(1); }
  50% { transform: scale(1.03); }
  to { transform: scale(1); }
}

/* =========================================
   3. HEADER & NAVIGATION
   ========================================= */
.site-header {
  position: sticky;
  top: 0;
  background: linear-gradient(90deg, rgba(2,6,15,0.6), rgba(6,8,16,0.35));
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  padding: 12px 0;
  border-bottom: 1px solid var(--glass-border);
  z-index: 100;
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.site-nav a {
  color: var(--muted);
  text-decoration: none;
  margin-left: 18px;
  padding: 8px 12px;
  border-radius: 6px;
  transition: all 0.2s ease;
}

.site-nav a.active, .site-nav a:hover {
  color: #fff;
  background: linear-gradient(90deg, rgba(89,240,255,0.1), rgba(59,120,255,0.05));
}

/* =========================================
   4. HERO & SHIMMER BRANDING
   ========================================= */
.hero { padding: 48px 0; }
.title { font-size: 42px; margin: 0 0 8px; letter-spacing: -0.5px; }
.tagline { color: var(--muted); font-size: 1.2rem; margin-top: 0; }

.shimmer-divider {
  display: inline-block;
  margin: 22px 0;
  padding: 12px 24px;
  border-radius: 12px;
  font-weight: 700;
  color: #dff8ff;
  position: relative;
  overflow: hidden;
  background: rgba(10, 30, 60, 0.4);
  border: 1px solid var(--glass-border);
}

.shimmer-divider::after {
  content: '';
  position: absolute;
  left: -100%;
  top: 0;
  bottom: 0;
  width: 60%;
  background: linear-gradient(90deg, transparent, rgba(180,240,255,0.3), transparent);
  animation: shimmer 3s infinite;
  transform: skewX(-20deg);
}

@keyframes shimmer {
  0% { left: -100%; }
  100% { left: 200%; }
}

/* =========================================
   5. CARDS & SECTIONS
   ========================================= */
.card {
  background: linear-gradient(180deg, var(--glass), rgba(255,255,255,0.01));
  padding: 28px;
  border-radius: 16px;
  margin-top: 24px;
  backdrop-filter: blur(10px);
  border: 1px solid var(--glass-border);
  box-shadow: 0 10px 40px rgba(0,0,0,0.4);
}

h2 { color: var(--accent); margin-top: 0; font-size: 1.8rem; }
h3 { color: #cfffff; margin: 24px 0 12px; }

/* =========================================
   6. THE HOVER DICTIONARY (TOOLTIPS)
   ========================================= */
.var-tip {
  position: relative;
  display: inline-block;
  color: var(--accent);
  cursor: help;
  font-weight: 600;
  border-bottom: 1px dotted rgba(89,240,255,0.4);
  padding: 0 2px;
  transition: background 0.2s ease;
}

.var-tip:hover {
  background: rgba(89, 240, 255, 0.1);
  border-radius: 4px;
}

.var-tip::after {
  content: attr(data-tip);
  position: absolute;
  bottom: 140%;
  left: 50%;
  transform: translateX(-50%) scale(0.9);
  background: #0a0a1a;
  color: #fff;
  padding: 8px 14px;
  border-radius: 8px;
  border: 1px solid var(--accent);
  font-size: 0.85rem;
  font-weight: 400;
  white-space: nowrap;
  opacity: 0;
  visibility: hidden;
  transition: all 0.2s cubic-bezier(0.175, 0.885, 0.32, 1.275);
  z-index: 1000;
  box-shadow: 0 10px 30px rgba(0,0,0,0.8);
  pointer-events: none;
}

.var-tip:hover::after {
  opacity: 1;
  visibility: visible;
  transform: translateX(-50%) scale(1) translateY(-5px);
}

/* =========================================
   7. EQUATIONS & THEORY BLOCKS
   ========================================= */
.equation {
  display: inline-block;
  padding: 14px 20px;
  border-radius: 12px;
  background: rgba(0, 8, 18, 0.7);
  border: 1px solid rgba(89, 240, 255, 0.1);
  color: #bffaff;
  font-weight: 500;
  font-size: 1.4rem;
  margin: 16px 0;
  font-family: 'Inter', monospace;
  box-shadow: inset 0 2px 10px rgba(0,0,0,0.5);
}

.derivation-tree {
  font-family: 'JetBrains Mono', monospace;
  line-height: 2.2;
  background: rgba(0,0,0,0.3);
  padding: 24px;
  border-radius: 14px;
  border-left: 3px solid var(--accent);
}

.example {
  background: rgba(255,255,255,0.02);
  padding: 1.2em 1.6em;
  border-radius: 10px;
  margin: 1.5em 0;
  border-left: 2px solid var(--accent);
  font-style: italic;
  color: #d1e5ff;
}

.example::before { content: "➤ "; color: var(--accent); font-weight: bold; }

/* =========================================
   8. UTILITIES & RESPONSIVENESS
   ========================================= */
.muted { color: var(--muted); }

.site-footer {
  padding: 40px 0;
  margin-top: 40px;
  border-top: 1px solid var(--glass-border);
  color: var(--muted);
  text-align: center;
  font-size: 0.9rem;
}

@media (max-width: 700px) {
  .container { padding: 16px; }
  .title { font-size: 32px; }
  .equation { font-size: 1.1rem; width: 100%; text-align: center; }
  .var-tip::after { white-space: normal; width: 200px; text-align: center; }
}