/* ============================================================
   ChessMaster Academy — Global Design System
   Dark chess theme with gold accents and glassmorphism
   ============================================================ */

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

/* ── CSS Variables ───────────────────────────────────────── */
:root {
  --bg-primary:    #030712; /* Obsidian */
  --bg-secondary:  #0b0f1a;
  --bg-card:       rgba(255, 255, 255, 0.035);
  --bg-glass:      rgba(3, 7, 18, 0.65);
  --bg-hover:      rgba(255, 255, 255, 0.08);

  --gold:          #f5c842;
  --gold-light:    #fde68a;
  --gold-dark:     #d4a017;

  --accent-blue:   #3b82f6;
  --accent-green:  #22c55e;
  --accent-red:    #ef4444;
  --accent-purple: #8b5cf6;
  --accent-amber:  #f59e0b;

  --text-primary:  #ffffff; /* Maximum contrast white */
  --text-secondary:#cbd5e1; /* Brighter grey for readability */
  --text-muted:    #94a3b8; /* Brighter muted for readability */

  --border:        rgba(255,255,255,0.08);
  --border-gold:   rgba(245,200,66,0.35);

  --diff-beginner: #22c55e;
  --diff-medium:   #f59e0b;
  --diff-hard:     #ef4444;
  --diff-advanced: #8b5cf6;

  --sidebar-w:     260px;
  --topbar-h:      72px;
  --radius:        12px;
  --radius-lg:     24px;
  --shadow:        0 20px 50px -12px rgba(0, 0, 0, 0.8);
  --shadow-gold:   0 0 30px rgba(245, 200, 66, 0.12);
  --transition:    all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --font-header:   'Outfit', sans-serif;
  --font-body:     'Inter', sans-serif;
  --bg-premium:    linear-gradient(135deg, #030712 0%, #080c17 100%);
}

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

html { scroll-behavior: smooth; }

body {
  font-family: var(--font-body);
  background: var(--bg-primary);
  color: var(--text-primary);
  min-height: 100vh;
  line-height: 1.6;
  overflow-x: hidden;
}

/* Kinetic Background System */
.kinetic-wrap {
  position: fixed; inset: 0; z-index: -1; overflow: hidden;
  background: radial-gradient(circle at 50% 50%, #0a0a0c 0%, #030712 100%);
}
.kinetic-piece {
  position: absolute; opacity: 0.12; pointer-events: none;
  filter: blur(1px) brightness(0.8);
  animation: float-drift 20s infinite linear;
}
@keyframes float-drift {
  0% { transform: translate(0, 0) rotate(0deg); }
  33% { transform: translate(30px, -50px) rotate(10deg); }
  66% { transform: translate(-20px, 20px) rotate(-10deg); }
  100% { transform: translate(0, 0) rotate(0deg); }
}

.floating-pawn { width: 120px; top: 15%; left: 10%; animation-duration: 25s; }
.floating-knight { width: 180px; bottom: 10%; right: 15%; animation-duration: 35s; animation-delay: -5s; }
.floating-king { width: 220px; top: -5%; right: 5%; opacity: 0.08; filter: blur(3px); animation-duration: 45s; }
.floating-queen { width: 150px; bottom: 15%; left: 5%; animation-duration: 30s; animation-delay: -10s; }

.nebula-glow {
  position: absolute; width: 600px; height: 600px;
  background: radial-gradient(circle, rgba(245,200,66,0.05) 0%, transparent 70%);
  border-radius: 50%; filter: blur(80px);
  animation: nebula-pulse 15s infinite alternate ease-in-out;
}
@keyframes nebula-pulse { 0% { transform: scale(1) translate(0,0); opacity: 0.3; } 100% { transform: scale(1.5) translate(50px,50px); opacity: 0.6; } }

/* Premium Background Utility */
.premium-bg {
    position: fixed; inset: 0; z-index: -1;
    background: radial-gradient(circle at top right, rgba(245,200,66,0.04), transparent 40%),
                radial-gradient(circle at bottom left, rgba(59,130,246,0.04), transparent 40%),
                var(--bg-premium);
    pointer-events: none;
}

/* Enhanced Glassmorphism */
.glass-panel {
    background: rgba(15, 23, 42, 0.65);
    backdrop-filter: blur(24px);
    -webkit-backdrop-filter: blur(24px);
    border: 1px solid rgba(255, 255, 255, 0.08);
    border-radius: var(--radius-lg);
    box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.5);
}

.glass-card {
    background: rgba(255, 255, 255, 0.03);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border: 1px solid rgba(255, 255, 255, 0.05);
    border-radius: var(--radius);
    transition: var(--transition);
}
.glass-card:hover {
    background: rgba(255, 255, 255, 0.06);
    border-color: var(--border-gold);
    transform: translateY(-2px);
    box-shadow: var(--shadow-gold);
}

a { color: var(--gold); text-decoration: none; transition: var(--transition); }
a:hover { color: var(--gold-light); }

img { max-width: 100%; display: block; }

/* ── Typography ─────────────────────────────────────────── */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-header);
  line-height: 1.3;
  color: var(--text-primary);
}
h1 { font-size: 2.25rem; }
h2 { font-size: 1.75rem; }
h3 { font-size: 1.35rem; }

/* ── 3D Cinematic Transitions ─────────────────────────────── */
.cinematic-transition {
  perspective: 1000px;
  overflow: hidden;
}
.cinematic-slide {
  transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1), opacity 0.6s ease;
  transform-style: preserve-3d;
}
.slide-out-left { transform: rotateY(-15deg) translateX(-100%); opacity: 0; }
.slide-in-right { transform: rotateY(15deg) translateX(100%); opacity: 0; }

/* Cinematic Walkthrough Sidepanel */
.cinematic-walkthrough {
  background: linear-gradient(180deg, rgba(20,20,20,0.8), rgba(10,10,10,0.95));
  border: 1px solid var(--border-gold);
  border-radius: 12px;
  padding: 1.5rem;
  margin-top: 1.5rem;
  box-shadow: 0 0 30px rgba(245,200,66,0.05);
  position: relative;
  overflow: hidden;
}
.walkthrough-header {
  font-size: 0.7rem;
  font-weight: 800;
  color: var(--gold);
  text-transform: uppercase;
  letter-spacing: 2px;
  margin-bottom: 0.75rem;
  display: flex; align-items: center; gap: 8px;
}
.walkthrough-content {
  font-size: 0.9rem;
  line-height: 1.6;
  color: var(--text-primary);
  min-height: 80px;
}
.walkthrough-ticker {
  background: rgba(0,0,0,0.3);
  border-top: 1px solid var(--border);
  padding: 0.5rem 1rem;
  font-family: 'Courier New', Courier, monospace;
  font-size: 0.75rem;
  color: var(--accent-green);
  white-space: nowrap;
  overflow: hidden;
}

/* Sidebar Tech Path */
.tech-path-item {
  position: relative;
  padding-left: 2rem !important;
}
.tech-path-item::before {
  content: '';
  position: absolute;
  left: 0.75rem; top: 0; bottom: 0;
  width: 2px;
  background: var(--border);
  opacity: 0.3;
}
.tech-path-item.active::before {
  background: var(--gold);
  opacity: 1;
  box-shadow: 0 0 10px var(--gold);
}
.tech-path-node {
  position: absolute;
  left: 0.45rem; top: 50%;
  width: 10px; height: 10px;
  background: var(--bg-body);
  border: 2px solid var(--border);
  border-radius: 50%;
  transform: translateY(-50%);
  z-index: 2;
}
.tech-path-item.active .tech-path-node {
  border-color: var(--gold);
  background: var(--gold);
  box-shadow: 0 0 8px var(--gold);
}

.text-gold    { color: var(--gold); }
.text-muted   { color: var(--text-secondary); }
.text-sm      { font-size: 0.875rem; }
.text-xs      { font-size: 0.75rem; }
.text-center  { text-align: center; }
.font-bold    { font-weight: 700; }
.font-semi    { font-weight: 600; }

/* ── Layout ─────────────────────────────────────────────── */
.app-layout {
  display: flex;
  min-height: 100vh;
}

.main-content {
  flex: 1;
  margin-left: var(--sidebar-w);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

@media (max-width: 991px) {
  .main-content { margin-left: 0; }
}

.page-content {
  flex: 1;
  padding: 2rem;
  margin-top: var(--topbar-h);
}

@media (max-width: 768px) {
  .page-content { padding: 1.25rem; }
}

/* ── Page Header ────────────────────────────────────────── */
.page-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 2rem;
}
.page-header-title {
  font-family: 'Playfair Display', serif;
  font-size: 2.2rem;
  font-weight: 800;
  color: #fff;
  margin-bottom: 0.25rem;
  line-height: 1.2;
}
.page-header-sub {
  font-size: 0.95rem;
  color: var(--text-muted);
}

/* ── Topbar ─────────────────────────────────────────────── */
.topbar {
  position: fixed;
  top: 0;
  left: var(--sidebar-w);
  right: 0;
  height: var(--topbar-h);
  background: rgba(15,17,23,0.92);
  backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  padding: 0 2rem;
  z-index: 100;
  gap: 1rem;
}

@media (max-width: 991px) {
  .topbar { left: 0; padding: 0 1.25rem; }
}
.topbar-title {
  font-family: 'Playfair Display', serif;
  font-size: 1.1rem;
  color: var(--gold);
  font-weight: 700;
}
.topbar-spacer { flex: 1; }
.topbar-user {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  cursor: pointer;
  padding: 0.5rem 1rem;
  border-radius: 100px;
  border: 1px solid var(--border);
  transition: var(--transition);
}
.topbar-user:hover { background: var(--bg-hover); border-color: var(--border-gold); }
.topbar-avatar {
  width: 36px; height: 36px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--gold-dark), var(--gold));
  display: flex; align-items: center; justify-content: center;
  font-weight: 700; font-size: 0.875rem; color: #000;
}

/* ── Sidebar ─────────────────────────────────────────────── */
.sidebar {
  position: fixed;
  top: 0; left: 0; bottom: 0;
  width: var(--sidebar-w);
  background: var(--bg-secondary);
  border-right: 1px solid var(--border);
  overflow-y: auto;
  z-index: 200;
  display: flex;
  flex-direction: column;
}
.sidebar::-webkit-scrollbar { width: 4px; }
.sidebar::-webkit-scrollbar-track { background: transparent; }
.sidebar::-webkit-scrollbar-thumb { background: var(--border); border-radius: 4px; }

.sidebar-logo {
  padding: 1.25rem 1.5rem;
  border-bottom: 1px solid var(--border);
  display: flex; align-items: center; gap: 0.75rem;
}
.sidebar-logo-icon {
  width: 40px; height: 40px;
  background: linear-gradient(135deg, var(--gold-dark), var(--gold));
  border-radius: 10px;
  display: flex; align-items: center; justify-content: center;
  font-size: 1.4rem;
}
.sidebar-logo-text {
  font-family: 'Playfair Display', serif;
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--text-primary);
  line-height: 1.2;
}
.sidebar-logo-sub {
  font-size: 0.7rem;
  color: var(--text-muted);
  font-family: 'Outfit', sans-serif;
}

.sidebar-nav { padding: 1rem 0; flex: 1; }
.sidebar-section-title {
  padding: 0.5rem 1.5rem;
  font-size: 0.68rem;
  text-transform: uppercase;
  letter-spacing: 1.5px;
  color: var(--text-muted);
  font-weight: 600;
}

.sidebar-item {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.65rem 1.5rem;
  color: var(--text-secondary);
  font-size: 0.9rem;
  font-weight: 500;
  cursor: pointer;
  transition: var(--transition);
  border-left: 3px solid transparent;
  position: relative;
}
.sidebar-item:hover {
  color: var(--text-primary);
  background: var(--bg-hover);
  border-left-color: var(--border-gold);
}
.sidebar-item.active {
  color: var(--gold);
  background: rgba(245,200,66,0.08);
  border-left-color: var(--gold);
}
.sidebar-item-icon { font-size: 1.1rem; width: 22px; text-align: center; }
.sidebar-badge {
  margin-left: auto;
  background: var(--accent-red);
  color: #fff;
  font-size: 0.65rem;
  font-weight: 700;
  padding: 1px 7px;
  border-radius: 100px;
}

.sidebar-footer {
  padding: 1rem 1.5rem;
  border-top: 1px solid var(--border);
}

/* ── Cards ──────────────────────────────────────────────── */
.card {
  background: var(--bg-card);
  backdrop-filter: blur(24px);
  -webkit-backdrop-filter: blur(24px);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 1.75rem;
  transition: var(--transition);
  box-shadow: var(--shadow);
}
.card:hover { 
    border-color: var(--border-gold); 
    box-shadow: 0 20px 50px rgba(0,0,0,0.6), var(--shadow-gold); 
    transform: translateY(-4px);
}

.card-glass {
  background: var(--bg-glass);
  backdrop-filter: blur(12px);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
}

/* 3D Tilt Effect */
.tilt-card {
  transition: transform 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275), box-shadow 0.3s ease;
  transform-style: preserve-3d;
  perspective: 1000px;
}
.tilt-card:hover {
  transform: translateY(-8px) rotateX(2deg) rotateY(2deg);
  box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.7), var(--shadow-gold);
}
.tilt-card > * { transform: translateZ(20px); }

.stat-card {
  background: var(--bg-card);
  backdrop-filter: blur(20px);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 1.75rem;
  display: flex; align-items: center; gap: 1.25rem;
  transition: var(--transition);
  position: relative;
  overflow: hidden;
  box-shadow: var(--shadow);
}
.stat-card::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 3px;
  background: linear-gradient(90deg, var(--gold-dark), var(--gold));
}
.stat-card:hover { border-color: var(--border-gold); transform: translateY(-2px); box-shadow: var(--shadow-gold); }

.stat-icon {
  width: 52px; height: 52px;
  border-radius: 12px;
  display: flex; align-items: center; justify-content: center;
  font-size: 1.5rem;
  flex-shrink: 0;
}
.stat-value { font-size: 1.8rem; font-weight: 800; font-family: 'Outfit', sans-serif; color: var(--text-primary); }
.stat-label { font-size: 0.8rem; color: var(--text-secondary); }
.stat-change { font-size: 0.75rem; margin-top: 0.25rem; }
.stat-change.up { color: var(--accent-green); }
.stat-change.down { color: var(--accent-red); }

/* ── Grid Layouts ───────────────────────────────────────── */
.grid-4 { display: grid; grid-template-columns: repeat(4, 1fr); gap: 1.25rem; }
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1.25rem; }
.grid-2 { display: grid; grid-template-columns: repeat(2, 1fr); gap: 1.25rem; }
.grid-auto { display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: 1.25rem; }

/* ── Buttons ─────────────────────────────────────────────── */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 0.5rem;
  padding: 0.6rem 1.25rem;
  border-radius: 8px;
  font-family: 'Outfit', sans-serif;
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  border: none;
  transition: var(--transition);
  text-decoration: none;
  white-space: nowrap;
}
.btn:hover { transform: translateY(-1px); }
.btn:active { transform: translateY(0); }

.btn-primary {
  background: linear-gradient(135deg, var(--gold-dark), var(--gold));
  color: #000;
}
.btn-primary:hover { box-shadow: 0 4px 20px rgba(245,200,66,0.4); color: #000; }

.btn-secondary {
  background: var(--bg-hover);
  color: var(--text-primary);
  border: 1px solid var(--border);
}
.btn-secondary:hover { border-color: var(--border-gold); color: var(--gold); }

.btn-success { background: var(--accent-green); color: #fff; }
.btn-danger  { background: var(--accent-red);   color: #fff; }
.btn-info    { background: var(--accent-blue);   color: #fff; }
.btn-purple  { background: var(--accent-purple); color: #fff; }

.btn-sm  { padding: 0.4rem 0.9rem; font-size: 0.8rem; }
.btn-xs  { padding: 0.25rem 0.6rem; font-size: 0.72rem; line-height: 1; border-radius: 4px; }
.btn-lg  { padding: 0.85rem 2rem;  font-size: 1rem; }
.btn-icon { padding: 0.5rem; width: 36px; height: 36px; border-radius: 8px; }

.btn-outline {
  background: transparent;
  border: 1px solid var(--border-gold);
  color: var(--gold);
}
.btn-outline:hover { background: rgba(245,200,66,0.1); color: var(--gold); }

.btn-outline-gold {
  background: transparent;
  border: 1px solid var(--gold);
  color: var(--gold);
  font-size: 0.75rem;
  padding: 0.3rem 0.6rem;
}
.btn-outline-gold:hover {
  background: var(--gold);
  color: #000;
  box-shadow: 0 0 10px rgba(245,200,66,0.3);
}

/* ── Forms ──────────────────────────────────────────────── */
.form-group { margin-bottom: 1.25rem; }
.form-label {
  display: block;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-secondary);
  margin-bottom: 0.5rem;
}
.form-control {
  width: 100%;
  padding: 0.65rem 1rem;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 8px;
  color: var(--text-primary);
  font-family: 'Outfit', sans-serif;
  font-size: 0.9rem;
  transition: var(--transition);
  outline: none;
}
.form-control:focus { border-color: var(--gold); box-shadow: 0 0 0 3px rgba(245,200,66,0.1); }
.form-control::placeholder { color: var(--text-muted); }

select.form-control { cursor: pointer; }
select.form-control option { background: var(--bg-card); }

textarea.form-control { min-height: 100px; resize: vertical; }

/* ── Tables ─────────────────────────────────────────────── */
.table-wrap { overflow-x: auto; }
.table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.9rem;
}
.table th {
  padding: 0.75rem 1rem;
  text-align: left;
  background: rgba(255,255,255,0.04);
  color: var(--text-secondary);
  font-weight: 600;
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  border-bottom: 1px solid var(--border);
}
.table td {
  padding: 0.85rem 1rem;
  border-bottom: 1px solid rgba(255,255,255,0.04);
  color: var(--text-primary);
  vertical-align: middle;
}
.table tbody tr { transition: var(--transition); }
.table tbody tr:hover { background: var(--bg-hover); }
.table tbody tr:last-child td { border-bottom: none; }

/* ── Badges ─────────────────────────────────────────────── */
.badge {
  display: inline-flex; align-items: center;
  padding: 0.2rem 0.6rem;
  border-radius: 100px;
  font-size: 0.72rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}
.badge-beginner  { background: rgba(34,197,94,0.15);  color: var(--diff-beginner); }
.badge-medium    { background: rgba(245,158,11,0.15); color: var(--diff-medium); }
.badge-hard      { background: rgba(239,68,68,0.15);  color: var(--diff-hard); }
.badge-advanced  { background: rgba(139,92,246,0.15); color: var(--diff-advanced); }
.badge-active    { background: rgba(34,197,94,0.15);  color: var(--accent-green); }
.badge-suspended { background: rgba(239,68,68,0.15);  color: var(--accent-red); }
.badge-admin     { background: rgba(245,200,66,0.15); color: var(--gold); }
.badge-teacher   { background: rgba(59,130,246,0.15); color: var(--accent-blue); }
.badge-student   { background: rgba(139,92,246,0.15); color: var(--accent-purple); }

/* ── Trophy Room & Badges ─────────────────────────────── */
.trophy-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(130px, 1fr));
  gap: 1rem;
  margin-top: 1rem;
}
.trophy-badge {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.25rem 0.75rem;
  text-align: center;
  transition: all 0.3s ease;
  position: relative;
  overflow: hidden;
  opacity: 0.4;
  filter: grayscale(1);
}
.trophy-badge.unlocked {
  opacity: 1;
  filter: none;
  border-color: var(--border-gold);
  background: linear-gradient(135deg, rgba(245,200,66,0.1), transparent);
}
.trophy-badge.unlocked:hover {
  transform: translateY(-5px) scale(1.05);
  box-shadow: 0 10px 20px rgba(0,0,0,0.4), 0 0 15px rgba(245,200,66,0.2);
}
.trophy-icon {
  font-size: 2.2rem;
  margin-bottom: 0.5rem;
  display: block;
}
.trophy-name {
  font-size: 0.72rem;
  font-weight: 800;
  color: var(--text-primary);
  text-transform: uppercase;
  letter-spacing: 1px;
}
.trophy-desc {
  font-size: 0.65rem;
  color: var(--text-muted);
  margin-top: 0.25rem;
}
.trophy-glow {
  position: absolute;
  inset: 0;
  background: radial-gradient(circle at center, rgba(245,200,66,0.15), transparent 70%);
  pointer-events: none;
  opacity: 0;
  transition: opacity 0.3s;
}
.trophy-badge.unlocked:hover .trophy-glow { opacity: 1; }

/* ── Progress Bar ───────────────────────────────────────── */
.progress {
  height: 8px;
  background: var(--bg-secondary);
  border-radius: 100px;
  overflow: hidden;
}
.progress-bar {
  height: 100%;
  background: linear-gradient(90deg, var(--gold-dark), var(--gold));
  border-radius: 100px;
  transition: width 0.6s ease;
}
.progress-green .progress-bar  { background: linear-gradient(90deg, #16a34a, var(--accent-green)); }
.progress-blue .progress-bar   { background: linear-gradient(90deg, #1d4ed8, var(--accent-blue)); }
.progress-purple .progress-bar { background: linear-gradient(90deg, #6d28d9, var(--accent-purple)); }

/* ── Alerts ─────────────────────────────────────────────── */
.alert {
  padding: 0.85rem 1.1rem;
  border-radius: var(--radius);
  display: flex; align-items: flex-start; gap: 0.75rem;
  font-size: 0.9rem;
  margin-bottom: 1rem;
}
.alert-success { background: rgba(34,197,94,0.12);  border: 1px solid rgba(34,197,94,0.25);  color: #86efac; }
.alert-error   { background: rgba(239,68,68,0.12);  border: 1px solid rgba(239,68,68,0.25);  color: #fca5a5; }
.alert-warning { background: rgba(245,158,11,0.12); border: 1px solid rgba(245,158,11,0.25); color: #fcd34d; }
.alert-info    { background: rgba(59,130,246,0.12); border: 1px solid rgba(59,130,246,0.25); color: #93c5fd; }

/* ── Timer ──────────────────────────────────────────────── */
.timer {
  display: inline-flex; align-items: center; gap: 0.5rem;
  padding: 0.5rem 1.1rem;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 8px;
  font-size: 1.4rem;
  font-weight: 700;
  font-family: 'Outfit', sans-serif;
  letter-spacing: 2px;
  color: var(--text-primary);
}
.timer.warning { border-color: var(--accent-amber); color: var(--accent-amber); animation: pulse 1s infinite; }
.timer.danger  { border-color: var(--accent-red);   color: var(--accent-red);   animation: pulse 0.5s infinite; }
@keyframes pulse { 0%,100% { opacity: 1; } 50% { opacity: 0.6; } }

/* ── Difficulty Filter Tabs ─────────────────────────────── */
.diff-tabs { display: flex; gap: 0.5rem; flex-wrap: wrap; margin-bottom: 1.5rem; }
.diff-tab {
  padding: 0.4rem 1rem;
  border-radius: 100px;
  border: 1px solid var(--border);
  background: transparent;
  color: var(--text-secondary);
  font-size: 0.83rem;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
}
.diff-tab[data-diff="beginner"].active, .diff-tab[data-diff="beginner"]:hover  { background:rgba(34,197,94,0.15); border-color:var(--diff-beginner); color:var(--diff-beginner); }
.diff-tab[data-diff="medium"].active, .diff-tab[data-diff="medium"]:hover      { background:rgba(245,158,11,0.15); border-color:var(--diff-medium); color:var(--diff-medium); }
.diff-tab[data-diff="hard"].active, .diff-tab[data-diff="hard"]:hover          { background:rgba(239,68,68,0.15); border-color:var(--diff-hard); color:var(--diff-hard); }
.diff-tab[data-diff="advanced"].active, .diff-tab[data-diff="advanced"]:hover  { background:rgba(139,92,246,0.15); border-color:var(--diff-advanced); color:var(--diff-advanced); }
.diff-tab[data-diff="all"].active, .diff-tab[data-diff="all"]:hover            { background:rgba(245,200,66,0.15); border-color:var(--gold); color:var(--gold); }

/* ── Page Header ─────────────────────────────────────────── */
.page-header {
  display: flex; align-items: center; justify-content: space-between;
  margin-bottom: 2rem;
  flex-wrap: wrap; gap: 1rem;
}
.page-header-title { font-size: 1.8rem; color: var(--text-primary); }
.page-header-sub { color: var(--text-secondary); font-size: 0.9rem; margin-top: 0.2rem; font-family: 'Outfit', sans-serif; }

/* ── Modal ──────────────────────────────────────────────── */
.modal-overlay {
  position: fixed; inset: 0;
  background: rgba(0,0,0,0.75);
  backdrop-filter: blur(4px);
  z-index: 1000;
  display: flex; align-items: center; justify-content: center;
  padding: 1rem;
  opacity: 0; pointer-events: none; transition: opacity 0.25s;
}
.modal-overlay.open { opacity: 1; pointer-events: all; }
.modal {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  width: 100%; max-width: 560px;
  max-height: 90vh;
  overflow-y: auto;
  transform: scale(0.95); transition: transform 0.25s;
}
.modal-overlay.open .modal { transform: scale(1); }
.modal-header {
  padding: 1.25rem 1.5rem;
  border-bottom: 1px solid var(--border);
  display: flex; align-items: center; justify-content: space-between;
}
.modal-title { font-family: 'Playfair Display', serif; font-size: 1.2rem; color: var(--text-primary); }
.modal-close {
  background: none; border: none; color: var(--text-muted);
  cursor: pointer; font-size: 1.4rem; padding: 0.25rem; transition: var(--transition);
}
.modal-close:hover { color: var(--accent-red); }
.modal-body { padding: 1.5rem; }
.modal-footer { padding: 1rem 1.5rem; border-top: 1px solid var(--border); display: flex; gap: 0.75rem; justify-content: flex-end; }

/* ── Chapter Card ─────────────────────────────────────────── */
.chapter-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 1.25rem;
  cursor: pointer;
  transition: var(--transition);
  display: flex; align-items: center; gap: 1rem;
  position: relative;
  overflow: hidden;
}
.chapter-card::after {
  content: '';
  position: absolute; top: 0; right: 0; bottom: 0;
  width: 4px;
  background: var(--border);
  transition: var(--transition);
}
.chapter-card:hover { border-color: var(--border-gold); transform: translateY(-2px); box-shadow: var(--shadow-gold); }
.chapter-card:hover::after { background: var(--gold); }
.chapter-card.completed::after { background: var(--accent-green); }
.chapter-card.locked { opacity: 0.5; cursor: not-allowed; }

.chapter-num {
  width: 40px; height: 40px; flex-shrink: 0;
  border-radius: 10px;
  background: var(--bg-secondary);
  display: flex; align-items: center; justify-content: center;
  font-weight: 800;
  font-size: 0.9rem;
  font-family: 'Outfit', sans-serif;
}
.chapter-info { flex: 1; min-width: 0; }
.chapter-title { font-family: 'Outfit', sans-serif; font-weight: 700; font-size: 0.92rem; color: var(--text-primary); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.chapter-meta { font-size: 0.75rem; color: var(--text-muted); margin-top: 0.2rem; }

/* ── Puzzle Board Wrapper ───────────────────────────────── */
.puzzle-layout {
  display: grid;
  grid-template-columns: auto 320px;
  gap: 1.5rem;
  align-items: start;
}
.board-wrap { position: relative; }
.board-container {
  width: 100%;
  max-width: 560px;
  aspect-ratio: 1;
  border-radius: var(--radius);
  overflow: hidden;
  border: 2px solid var(--border-gold);
  box-shadow: var(--shadow-gold);
}

/* ── Hint & Solution Panel ──────────────────────────────── */
.hint-panel {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  overflow: hidden;
}
.hint-panel-header {
  padding: 1rem 1.25rem;
  background: rgba(255,255,255,0.03);
  border-bottom: 1px solid var(--border);
  font-weight: 700;
  font-size: 0.9rem;
  display: flex; align-items: center; gap: 0.5rem;
}
.hint-panel-body { padding: 1.25rem; }

/* ── Leaderboard ─────────────────────────────────────────── */
.lb-item {
  display: flex; align-items: center; gap: 1rem;
  padding: 0.85rem 1rem;
  border-radius: var(--radius);
  transition: var(--transition);
}
.lb-item:hover { background: var(--bg-hover); }
.lb-rank {
  width: 32px; height: 32px;
  border-radius: 8px;
  display: flex; align-items: center; justify-content: center;
  font-weight: 800;
  font-size: 0.85rem;
  flex-shrink: 0;
  background: var(--bg-secondary);
  color: var(--text-secondary);
}
.lb-rank.gold   { background: linear-gradient(135deg,#d4a017,#f5c842); color:#000; }
.lb-rank.silver { background: linear-gradient(135deg,#6b7280,#9ca3af); color:#000; }
.lb-rank.bronze { background: linear-gradient(135deg,#b45309,#d97706); color:#fff; }

/* ── Animations ─────────────────────────────────────────── */
@keyframes fadeIn  { from { opacity:0; transform:translateY(12px); } to { opacity:1; transform:translateY(0); } }
@keyframes slideIn { from { transform:translateX(-20px); opacity:0; } to { transform:translateX(0); opacity:1; } }
@keyframes spin    { to { transform: rotate(360deg); } }
@keyframes bounce  { 0%,100% { transform:translateY(0); } 50% { transform:translateY(-6px); } }

.fade-in  { animation: fadeIn  0.4s ease both; }
.slide-in { animation: slideIn 0.3s ease both; }

/* ── Utilities ───────────────────────────────────────────── */
.flex        { display: flex; }
.items-center { align-items: center; }
.gap-1       { gap: 0.5rem; }
.gap-2       { gap: 1rem; }
.gap-3       { gap: 1.5rem; }
.mt-1 { margin-top: 0.5rem; }
.mt-2 { margin-top: 1rem; }
.mt-3 { margin-top: 1.5rem; }
.mt-4 { margin-top: 2rem; }
.mb-1 { margin-bottom: 0.5rem; }
.mb-2 { margin-bottom: 1rem; }
.mb-3 { margin-bottom: 1.5rem; }
.mb-4 { margin-bottom: 2rem; }
.p-0  { padding: 0; }
.w-full { width: 100%; }
.hidden { display: none !important; }
.divider { height: 1px; background: var(--border); margin: 1.25rem 0; }
.grid-auto {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1.25rem;
}
/* ── Curriculum Ultra-Dense Grid (Phase 24: Viewport Victory) ─ */
.grid-ultra {
  display: grid !important;
  grid-template-columns: repeat(6, 1fr) !important;
  gap: 1rem !important;
  padding: 1rem 0;
  width: 100% !important;
  max-width: 100% !important;
}
@media (max-width: 1440px) {
  .grid-ultra { grid-template-columns: repeat(4, 1fr) !important; }
}
@media (max-width: 1000px) {
  .grid-ultra { grid-template-columns: repeat(3, 1fr) !important; }
}
@media (max-width: 600px) {
  .grid-ultra { grid-template-columns: repeat(2, 1fr) !important; }
}

.grid-ultra-row {
  margin-bottom: 2.5rem;
  max-width: 100%;
  overflow: hidden;
}


.chapter-card-ultra {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.25rem 0.75rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  gap: 0.75rem;
  color: var(--text-primary);
  transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  min-height: 140px;
  position: relative;
  overflow: hidden;
}
.chapter-card-ultra::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 4px;
  background: var(--border);
  opacity: 0.2;
}
.chapter-card-ultra.completed::before { background: var(--accent-green); opacity: 1; }
.chapter-card-ultra.active::before    { background: var(--gold); opacity: 1; box-shadow: 0 0 10px var(--gold); }

.chapter-card-ultra:hover {
  background: rgba(245,200,66,0.03);
  border-color: var(--gold);
  transform: translateY(-5px);
  box-shadow: 0 10px 30px rgba(0,0,0,0.4), 0 0 15px rgba(245,200,66,0.1);
}
.chapter-card-ultra .icon-wrap {
  width: 44px;
  height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: rgba(255,255,255,0.03);
  border: 1px solid var(--border);
  border-radius: 12px;
  color: var(--gold);
  font-size: 1.4rem;
  transition: all 0.3s ease;
}
.chapter-card-ultra:hover .icon-wrap {
  background: var(--gold);
  color: #000;
  transform: scale(1.1) rotate(5deg);
}
.chapter-card-ultra .title {
  font-size: 0.85rem;
  font-weight: 700;
  line-height: 1.3;
  color: var(--text-primary);
  display: -webkit-box;
  -webkit-line-clamp: 2;
  line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}
.chapter-card-ultra .num-badge {
  font-size: 0.7rem;
  font-weight: 800;
  color: var(--text-muted);
  background: rgba(255,255,255,0.05);
  padding: 0.2rem 0.6rem;
  border-radius: 4px;
}
.chapter-card-ultra.completed { border-bottom: 2px solid rgba(34, 197, 94, 0.3); }
.chapter-card-ultra.completed .icon-wrap { border-color: var(--accent-green); color: var(--accent-green); background: rgba(34, 197, 94, 0.1); }
.chapter-card-ultra.active { border-color: var(--gold); background: rgba(245, 200, 66, 0.02); }
.chapter-card-ultra.active .icon-wrap { border-color: var(--gold); color: var(--gold); background: rgba(245, 200, 66, 0.1); }



/* Tiered Progress Bars */
.tier-progress-container {
  flex: 1;
  max-width: 200px;
  height: 4px;
  background: #333;
  border-radius: 10px;
  overflow: hidden;
  margin-left: auto;
}
.tier-progress-fill {
  height: 100%;
  background: var(--gold);
  border-radius: 10px;
  transition: width 1s ease-out;
}

/* ── Mini Chapter Cards ────────────────────────────────── */
.chapter-card-mini {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 0.75rem;
  display: flex;
  align-items: center;
  gap: 0.75rem;
  transition: all 0.3s ease;
  position: relative;
  overflow: hidden;
  cursor: pointer;
}
.chapter-card-mini:hover {
  border-color: var(--gold);
  transform: translateY(-2px);
  box-shadow: 0 5px 15px rgba(0,0,0,0.3);
}
.chapter-card-mini .num {
  font-size: 0.75rem;
  font-weight: 800;
  color: var(--text-muted);
  opacity: 0.5;
}
.chapter-card-mini .icon { font-size: 1.1rem; }
.chapter-card-mini .title {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--text-primary);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  flex: 1;
}
.chapter-card-mini.completed { border-left: 3px solid var(--accent-green); }

/* ── Board Visuals (Arrows/Highlights) ────────────────── */
.board-highlight {
  position: absolute;
  width: 12.5%; height: 12.5%;
  background: rgba(255, 255, 0, 0.3);
  pointer-events: none;
  z-index: 1;
}
.board-arrow {
  position: absolute;
  pointer-events: none;
  z-index: 10;
  filter: drop-shadow(0 0 2px rgba(0,0,0,0.5));
}

/* ── Move List ─────────────────────────────────────────── */
.move-list { font-family: 'Outfit', monospace; font-size: 0.85rem; overflow-y: auto; }
.move-pair { display: inline-flex; gap: 0.25rem; margin: 0.15rem 0; }
.move-num  { color: var(--text-muted); min-width: 24px; }
.move-san  { padding: 0.1rem 0.35rem; border-radius: 4px; color: var(--text-primary); cursor: pointer; }
.move-san:hover { background: rgba(245,200,66,0.15); color: var(--gold); }

/* ── Board Controls ─────────────────────────────────────── */
.board-controls { display: flex; gap: 0.5rem; margin-top: 0.75rem; flex-wrap: wrap; }
.board-btn {
  padding: 0.4rem 0.85rem;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 8px;
  color: var(--text-secondary);
  font-size: 0.82rem;
  font-family: 'Outfit', sans-serif;
  cursor: pointer;
  transition: var(--transition);
}
.board-btn:hover { border-color: var(--border-gold); color: var(--gold); }

/* ── Grandmaster Study Layout ───────────────────────────── */
.study-container {
  display: grid;
  grid-template-columns: 280px 1fr 360px;
  height: calc(100vh - var(--topbar-h));
  overflow: hidden;
  background: var(--bg-primary);
}

.study-sidebar {
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  background: rgba(15, 17, 23, 0.95);
}
.study-sidebar-header {
  padding: 1.25rem;
  border-bottom: 1px solid var(--border);
  font-weight: 700;
  font-size: 0.9rem;
  color: var(--gold);
  display: flex;
  justify-content: space-between;
}
.study-sidebar-list {
  flex: 1;
  overflow-y: auto;
  padding: 0.5rem;
}
.study-chapter-item {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.85rem 1rem;
  border-radius: 8px;
  margin-bottom: 4px;
  cursor: pointer;
  transition: var(--transition);
  color: var(--text-secondary);
  font-size: 0.88rem;
}
.study-chapter-item:hover { background: var(--bg-hover); color: var(--text-primary); }
.study-chapter-item.active { background: rgba(245,200,66,0.1); color: var(--gold); border: 1px solid var(--border-gold); }
.study-chapter-num { width: 24px; font-size: 0.75rem; font-weight: 800; opacity: 0.5; }

.study-center {
  padding: 2rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  position: relative;
  overflow-y: auto;
}
.study-board-wrap {
  width: 100%;
  max-width: 600px;
  aspect-ratio: 1;
  border: 4px solid var(--bg-card);
  border-radius: 12px;
  box-shadow: 0 0 50px rgba(0,0,0,0.5);
  position: relative;
}

.study-panel {
  border-left: 1px solid var(--border);
  background: var(--bg-secondary);
  display: flex;
  flex-direction: column;
}
.study-tabs {
  display: flex;
  border-bottom: 1px solid var(--border);
}
.study-tab {
  flex: 1;
  padding: 1rem;
  text-align: center;
  font-size: 0.8rem;
  font-weight: 700;
  cursor: pointer;
  color: var(--text-muted);
  border-bottom: 2px solid transparent;
  transition: var(--transition);
}
.study-tab:hover { color: var(--text-primary); }
.study-tab.active { color: var(--gold); border-bottom-color: var(--gold); background: rgba(255,255,255,0.02); }

.study-panel-content {
  flex: 1;
  overflow-y: auto;
  padding: 1.5rem;
}

.playback-controls {
  display: flex;
  gap: 0.5rem;
  margin-top: 1.5rem;
  background: var(--bg-card);
  padding: 0.6rem 1rem;
  border-radius: 100px;
  border: 1px solid var(--border);
}
.playback-btn {
  background: none; border: none; color: var(--text-secondary);
  font-size: 1.2rem; cursor: pointer; padding: 0.4rem;
  transition: var(--transition);
}
.playback-btn:hover { color: var(--gold); transform: scale(1.15); }

/* ── Responsive ─────────────────────────────────────────── */
/* ── Responsive ─────────────────────────────────────────── */
@media (max-width: 1024px) {
  :root { --sidebar-w: 220px; }
  .grid-4 { grid-template-columns: repeat(2, 1fr); }
  .grid-3 { grid-template-columns: repeat(2, 1fr); }
  .puzzle-layout { grid-template-columns: 1fr; }
}
@media (max-width: 768px) {
  :root { --sidebar-w: 0px; }
  .sidebar { transform: translateX(-100%); transition: transform 0.3s ease; }
  .sidebar.open { transform: translateX(0); width: 260px; }
  .main-content { margin-left: 0; }
  .topbar { left: 0; padding: 0 1rem; }
  .grid-4, .grid-3, .grid-2 { grid-template-columns: 1fr; }
  .page-content { padding: 1rem; margin-top: calc(var(--topbar-h) - 0.5rem); }
  .page-header-title { font-size: 1.4rem; }
  .page-header { flex-direction: column; align-items: flex-start; gap: 0.5rem; margin-bottom: 1.5rem; }
  .stat-card { padding: 1.25rem; gap: 1rem; }
  .stat-icon { width: 44px; height: 44px; font-size: 1.25rem; }
  .stat-value { font-size: 1.5rem; }
  .card { padding: 1.25rem; }
}
@media (max-width: 480px) {
  .topbar-user > div { display: none; } /* Hide user name on extremely small screens */
  .btn-lg { padding: 0.6rem 1.25rem; font-size: 0.9rem; }
}

/* ── Animations ─────────────────────────────────────────── */
@keyframes pulse {
  0%, 100% { opacity: 1; transform: scale(1); }
  50% { opacity: 0.6; transform: scale(0.92); }
}
.animate-pulse { animation: pulse 1.5s cubic-bezier(0.4, 0, 0.6, 1) infinite; }

/* ── Universal Responsiveness (Phase 20) ────────────────── */
@media (max-width: 1280px) {
  .study-container { flex-direction: column; height: auto; overflow-y: auto; padding: 1rem; }
  .study-sidebar { width: 100%; border-right: none; border-bottom: 1px solid var(--border); max-height: 250px; }
  .study-center { padding: 1.5rem 0; align-items: center; }
  .study-panel { width: 100%; border-left: none; border-top: 1px solid var(--border); height: auto; min-height: 400px; }
  .study-board-wrap { width: 100% !important; max-width: 100% !important; height: auto !important; aspect-ratio: 1; }
}

@media (max-width: 768px) {
  .grid-ultra { grid-template-columns: repeat(auto-fill, minmax(110px, 1fr)); }
  .chapter-card-ultra { padding: 0.4rem; font-size: 0.7rem; min-height: 40px; }
  .chapter-card-ultra .icon { font-size: 0.9rem; }
  .tier-progress-container { display: none; } /* Hide tier progress on small mobile */
  .roadmap-container { padding: 2rem 1rem; gap: 1.5rem; }
  .roadmap-node { width: 90px; }
  .node-circle { width: 48px; height: 48px; font-size: 1.2rem; }
}