/* Reset & Base Setup */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  background-color: var(--bg-primary);
  color: var(--text-primary);
  font-family: var(--font-main);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  scroll-behavior: auto;
  overflow-x: hidden;
  transition: var(--theme-transition);
}

body {
  position: relative;
  width: 100%;
  min-height: 100vh;
  overflow-x: hidden;
  line-height: 1.6;
  background-color: var(--bg-primary);
  color: var(--text-primary);
  transition: var(--theme-transition);
}

/* Background Subtle Mathematical Grid Pattern */
body::before {
  content: '';
  position: fixed;
  inset: 0;
  background-image: 
    linear-gradient(to right, var(--grid-line) 1px, transparent 1px),
    linear-gradient(to bottom, var(--grid-line) 1px, transparent 1px);
  background-size: 60px 60px;
  pointer-events: none;
  z-index: 0;
  opacity: 0.7;
  transition: opacity 0.4s ease;
}

/* Custom Selection */
::selection {
  background-color: var(--accent-blue);
  color: #FFFFFF;
}

/* Typography Hierarchy */
h1, h2, h3, h4, h5, h6 {
  color: var(--text-primary);
  font-weight: 600;
  line-height: 1.15;
  letter-spacing: -0.03em;
  transition: color 0.4s ease;
}

p {
  color: var(--text-secondary);
  font-size: clamp(1rem, 1.2vw, 1.25rem);
  font-weight: 400;
  line-height: 1.7;
  transition: color 0.4s ease;
}

a {
  color: inherit;
  text-decoration: none;
  transition: color 0.25s ease;
}

/* Container */
.container {
  width: 100%;
  max-width: var(--container-max-width);
  margin-left: auto;
  margin-right: auto;
  padding-left: var(--container-padding);
  padding-right: var(--container-padding);
  position: relative;
  z-index: 2;
}

/* Mathematical Labels & Chips */
.math-tag {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.15em;
  color: var(--accent-blue);
  font-weight: 600;
  padding: 0.35rem 0.85rem;
  border-radius: 999px;
  background: var(--accent-blue-subtle);
  border: 1px solid var(--border-blue);
  margin-bottom: 1.5rem;
  transition: var(--theme-transition);
}

.math-tag::before {
  content: '';
  display: inline-block;
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background-color: var(--accent-blue);
}

.section-label {
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--text-muted);
  display: block;
  margin-bottom: 1.25rem;
  transition: color 0.4s ease;
}

/* Editorial Buttons with Tactile & Magnetic Physics */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.75rem;
  padding: 1rem 2rem;
  font-family: var(--font-main);
  font-size: 0.95rem;
  font-weight: 600;
  border-radius: 999px;
  cursor: pointer;
  transition: transform 0.25s var(--transition-smooth), background-color 0.3s ease, border-color 0.3s ease, box-shadow 0.3s ease;
  border: none;
  text-decoration: none;
  position: relative;
  overflow: hidden;
  transform: translate3d(0, 0, 0);
  will-change: transform;
}

.btn:hover {
  transform: scale(1.02);
}

.btn:active {
  transform: scale(0.97);
}

.btn-primary {
  background-color: var(--text-primary);
  color: var(--text-inverse);
  box-shadow: 0 4px 14px rgba(18, 18, 20, 0.15);
}

.btn-primary:hover {
  background-color: var(--accent-blue);
  color: #FFFFFF;
  box-shadow: 0 8px 24px var(--accent-blue-glow);
}

.btn-secondary {
  background-color: transparent;
  color: var(--text-primary);
  border: 1px solid var(--border-strong);
}

.btn-secondary:hover {
  background-color: var(--bg-surface-subtle);
  border-color: var(--accent-teal);
  color: var(--text-primary);
}

.btn-arrow {
  transition: transform 0.3s var(--transition-smooth);
}

.btn:hover .btn-arrow {
  transform: translateX(4px);
}

/* Nav Controls: Theme Toggle & Sound Toggle */
.nav-controls-group {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.theme-toggle-btn, .sound-toggle-btn {
  background: var(--bg-surface-subtle);
  border: 1px solid var(--border-subtle);
  border-radius: 999px;
  width: 38px;
  height: 38px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  color: var(--text-primary);
  transition: transform 0.25s var(--transition-smooth), background-color 0.3s ease, border-color 0.3s ease, color 0.3s ease;
  position: relative;
  outline: none;
  transform: translate3d(0, 0, 0);
  will-change: transform;
}

.sound-toggle-btn {
  width: auto;
  padding: 0 0.85rem;
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.1em;
  gap: 0.4rem;
}

.theme-toggle-btn:hover, .sound-toggle-btn:hover {
  background: var(--bg-surface);
  border-color: var(--border-teal);
  color: var(--accent-teal);
  transform: scale(1.03);
}

.theme-toggle-btn:active, .sound-toggle-btn:active {
  transform: scale(0.97);
}

.theme-icon {
  width: 17px;
  height: 17px;
  stroke: currentColor;
  stroke-width: 2;
  fill: none;
  stroke-linecap: round;
  stroke-linejoin: round;
  transition: transform 0.5s var(--transition-bounce), opacity 0.3s ease;
}

.sound-dot {
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background-color: var(--accent-teal); /* Soft teal when active */
  transition: background-color 0.3s ease;
}

.sound-dot.muted {
  background-color: var(--text-muted);
}

/* Custom Interactive Cursor Dot */
.custom-cursor {
  position: fixed;
  top: 0;
  left: 0;
  width: 8px;
  height: 8px;
  background-color: var(--accent-blue);
  border-radius: 50%;
  pointer-events: none;
  z-index: 9999;
  transform: translate(-50%, -50%);
  transition: width 0.3s var(--transition-smooth), height 0.3s var(--transition-smooth), background-color 0.3s;
}

.custom-cursor-follower {
  position: fixed;
  top: 0;
  left: 0;
  width: 36px;
  height: 36px;
  border: 1px solid var(--border-teal);
  border-radius: 50%;
  pointer-events: none;
  z-index: 9998;
  transform: translate(-50%, -50%);
  transition: transform 0.08s linear, width 0.3s var(--transition-smooth), height 0.3s var(--transition-smooth), border-color 0.3s;
}

body:hover .custom-cursor.active {
  width: 14px;
  height: 14px;
  background-color: var(--accent-teal);
}

body:hover .custom-cursor-follower.active {
  width: 54px;
  height: 54px;
  border-color: var(--accent-blue);
}