/* ==========================================================================
   Brain Focus Books™ - Custom Design System & Interactive Styling
   Theme: Dark Cognitive Fitness (#0A1128, #121212, #00E5FF, #FF5722)
   ========================================================================== */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800&family=Montserrat:wght@500;600;700;800;900&family=JetBrains+Mono:wght@500;700&display=swap');

:root {
  --bg-midnight: #0A1128;
  --bg-charcoal: #121212;
  --bg-card: #141E38;
  --bg-card-hover: #1B294E;
  --cyan-electric: #00E5FF;
  --cyan-glow: rgba(0, 229, 255, 0.35);
  --coral-primary: #FF5722;
  --coral-hover: #FF7043;
  --coral-glow: rgba(255, 87, 34, 0.4);
  --text-white: #FFFFFF;
  --text-slate: #94A3B8;
  --text-muted: #64748B;
  
  /* Series Accent Palette */
  --series-4x4: #1E40AF;
  --series-5x5: #047857;
  --series-6x6: #0E7490;
  --series-medium: #D97706;
  --series-hard: #B91C1C;
  --series-senior: #6D28D9;
}

body {
  font-family: 'Inter', sans-serif;
  background-color: var(--bg-midnight);
  color: var(--text-white);
  overflow-x: hidden;
}

h1, h2, h3, h4, h5, h6, .font-heading {
  font-family: 'Montserrat', sans-serif;
}

.font-mono-calc {
  font-family: 'JetBrains Mono', monospace;
}

/* Custom Scrollbar */
::-webkit-scrollbar {
  width: 10px;
}
::-webkit-scrollbar-track {
  background: #070B1A;
}
::-webkit-scrollbar-thumb {
  background: #1E293B;
  border-radius: 5px;
  border: 2px solid #070B1A;
}
::-webkit-scrollbar-thumb:hover {
  background: var(--cyan-electric);
}

/* Background Cognitive Grid Pattern */
.bg-cognitive-grid {
  background-image: 
    radial-gradient(circle at 50% 0%, rgba(0, 229, 255, 0.12) 0%, transparent 60%),
    radial-gradient(circle at 100% 50%, rgba(255, 87, 34, 0.08) 0%, transparent 50%),
    linear-gradient(to right, rgba(255, 255, 255, 0.03) 1px, transparent 1px),
    linear-gradient(to bottom, rgba(255, 255, 255, 0.03) 1px, transparent 1px);
  background-size: 100% 100%, 100% 100%, 36px 36px, 36px 36px;
}

/* Glowing Neon Elements */
.glow-cyan-box {
  box-shadow: 0 0 25px -5px var(--cyan-glow);
  border: 1px solid rgba(0, 229, 255, 0.4);
}

.glow-cyan-box:hover {
  box-shadow: 0 0 35px 0px rgba(0, 229, 255, 0.6);
  border-color: var(--cyan-electric);
}

.glow-coral-btn {
  background-color: var(--coral-primary);
  box-shadow: 0 4px 20px -2px var(--coral-glow);
  transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

.glow-coral-btn:hover {
  background-color: var(--coral-hover);
  box-shadow: 0 6px 28px 0px rgba(255, 87, 34, 0.6);
  transform: translateY(-2px);
}

.glow-cyan-text {
  text-shadow: 0 0 16px rgba(0, 229, 255, 0.6);
}

.text-gradient-cyan {
  background: linear-gradient(135deg, #FFFFFF 30%, #00E5FF 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.text-gradient-coral {
  background: linear-gradient(135deg, #FF8A65 0%, #FF5722 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

/* 3D Realistic Book Component */
.book-wrapper {
  perspective: 1200px;
}

.book-card-3d {
  position: relative;
  width: 200px;
  height: 285px;
  transform-style: preserve-3d;
  transform: rotateY(-18deg) rotateX(8deg) translateZ(0);
  transition: transform 0.4s ease, box-shadow 0.4s ease;
}

.book-wrapper:hover .book-card-3d {
  transform: rotateY(-4deg) rotateX(2deg) scale(1.04) translateZ(12px);
}

.book-cover {
  position: absolute;
  inset: 0;
  border-radius: 3px 8px 8px 3px;
  overflow: hidden;
  box-shadow: 
    -12px 14px 28px rgba(0, 0, 0, 0.7),
    -3px 0 6px rgba(0, 0, 0, 0.4),
    inset 4px 0 8px rgba(255, 255, 255, 0.15),
    inset -3px 0 5px rgba(0, 0, 0, 0.6);
  background: linear-gradient(135deg, #10162B 0%, #0A0E1E 100%);
  border: 1px solid rgba(255, 255, 255, 0.1);
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  padding: 14px;
}

.book-spine-shine {
  position: absolute;
  top: 0;
  left: 0;
  bottom: 0;
  width: 14px;
  background: linear-gradient(
    90deg, 
    rgba(255, 255, 255, 0.35) 0%, 
    rgba(255, 255, 255, 0.05) 30%, 
    rgba(0, 0, 0, 0.4) 70%, 
    rgba(255, 255, 255, 0.15) 100%
  );
  z-index: 10;
  pointer-events: none;
}

.book-pages-side {
  position: absolute;
  top: 4px;
  right: -9px;
  width: 9px;
  height: calc(100% - 8px);
  background: repeating-linear-gradient(
    to right,
    #E2E8F0,
    #CBD5E1 1px,
    #94A3B8 2px
  );
  transform: rotateY(90deg) translateZ(-4px);
  border-radius: 0 2px 2px 0;
  box-shadow: 2px 4px 6px rgba(0,0,0,0.5);
}

/* Large Hero 3D Book */
.hero-book-card-3d {
  position: relative;
  width: 270px;
  height: 380px;
  transform-style: preserve-3d;
  transform: rotateY(-20deg) rotateX(8deg);
  transition: transform 0.5s cubic-bezier(0.2, 0.8, 0.2, 1);
  animation: heroBookFloat 6s ease-in-out infinite alternate;
}

@keyframes heroBookFloat {
  0% {
    transform: rotateY(-20deg) rotateX(8deg) translateY(0px);
  }
  100% {
    transform: rotateY(-14deg) rotateX(4deg) translateY(-14px);
  }
}

/* Calcudoku Grid Styling */
.calcudoku-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-template-rows: repeat(4, 1fr);
  background-color: #070C1B;
  border: 3px solid var(--cyan-electric);
  box-shadow: 0 0 25px rgba(0, 229, 255, 0.3);
  border-radius: 8px;
  overflow: hidden;
  user-select: none;
}

.calcudoku-cell {
  position: relative;
  width: 100%;
  aspect-ratio: 1 / 1;
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: 'Montserrat', sans-serif;
  font-weight: 700;
  font-size: 1.5rem;
  color: #FFFFFF;
  background-color: #0D162F;
  cursor: pointer;
  transition: background-color 0.15s ease, color 0.15s ease, transform 0.1s ease;
  border: 1px solid rgba(255, 255, 255, 0.08);
}

.calcudoku-cell:hover {
  background-color: #17244B;
}

.calcudoku-cell.selected {
  background-color: #1D3268;
  outline: 2px solid var(--cyan-electric);
  outline-offset: -2px;
  z-index: 5;
}

.calcudoku-cell.error {
  background-color: rgba(239, 68, 68, 0.25);
  color: #FCA5A5;
  animation: shake 0.3s ease-in-out;
}

.calcudoku-cell.correct {
  background-color: rgba(16, 185, 129, 0.25);
  color: #6EE7B7;
}

.calcudoku-cell.same-num {
  background-color: #19274F;
}

/* Cage Clue Label */
.cage-label {
  position: absolute;
  top: 2px;
  left: 4px;
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.68rem;
  font-weight: 700;
  color: var(--cyan-electric);
  line-height: 1;
  pointer-events: none;
  z-index: 2;
  text-shadow: 0 1px 2px rgba(0,0,0,0.8);
}

/* Specific Cage Boundary Borders */
.border-top-thick { border-top: 3px solid #00E5FF !important; }
.border-bottom-thick { border-bottom: 3px solid #00E5FF !important; }
.border-left-thick { border-left: 3px solid #00E5FF !important; }
.border-right-thick { border-right: 3px solid #00E5FF !important; }

.border-top-thin { border-top: 1px dashed rgba(255, 255, 255, 0.15); }
.border-bottom-thin { border-bottom: 1px dashed rgba(255, 255, 255, 0.15); }
.border-left-thin { border-left: 1px dashed rgba(255, 255, 255, 0.15); }
.border-right-thin { border-right: 1px dashed rgba(255, 255, 255, 0.15); }

/* Animation Keyframes */
@keyframes shake {
  0%, 100% { transform: translateX(0); }
  20%, 60% { transform: translateX(-4px); }
  40%, 80% { transform: translateX(4px); }
}

@keyframes pulseGlow {
  0% { box-shadow: 0 0 15px rgba(0, 229, 255, 0.3); }
  50% { box-shadow: 0 0 30px rgba(0, 229, 255, 0.7); }
  100% { box-shadow: 0 0 15px rgba(0, 229, 255, 0.3); }
}

.pulse-glow {
  animation: pulseGlow 3s infinite ease-in-out;
}

/* Pill Badges */
.pill-badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 4px 12px;
  border-radius: 9999px;
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.pill-cyan {
  background: rgba(0, 229, 255, 0.12);
  color: var(--cyan-electric);
  border: 1px solid rgba(0, 229, 255, 0.3);
}

.pill-coral {
  background: rgba(255, 87, 34, 0.15);
  color: #FF8A65;
  border: 1px solid rgba(255, 87, 34, 0.4);
}

/* Modal Backdrop & Animation */
.modal-backdrop {
  background: rgba(6, 11, 25, 0.85);
  backdrop-filter: blur(8px);
}

.modal-enter {
  animation: modalEnter 0.25s cubic-bezier(0.16, 1, 0.3, 1) forwards;
}

@keyframes modalEnter {
  from {
    opacity: 0;
    transform: scale(0.95) translateY(10px);
  }
  to {
    opacity: 1;
    transform: scale(1) translateY(0);
  }
}

/* Confetti particles */
.confetti-particle {
  position: absolute;
  width: 8px;
  height: 8px;
  border-radius: 2px;
  pointer-events: none;
  animation: confettiFall 2.5s ease-out forwards;
}

@keyframes confettiFall {
  0% {
    transform: translate(0, 0) rotate(0deg) scale(1);
    opacity: 1;
  }
  100% {
    transform: translate(var(--dx), var(--dy)) rotate(var(--rot)) scale(0.2);
    opacity: 0;
  }
}