/* === Hat Study Hub — Theme: MMORPG vibes === */
:root {
  --bg-primary: #0a0e1a;
  --bg-secondary: #131829;
  --bg-card: #1a2138;
  --bg-card-hover: #232c47;
  --border: #2a3553;
  --border-hover: #4a5b8c;
  --text-primary: #e8ecf4;
  --text-secondary: #8b95b2;
  --text-muted: #586079;
  --accent: #7c5cff;
  --accent-glow: rgba(124, 92, 255, 0.4);
  --gold: #ffc857;
  --gold-glow: rgba(255, 200, 87, 0.4);
  --green: #4ade80;
  --red: #f87171;
  --orange: #fb923c;
  --blue: #60a5fa;
  --shadow-card: 0 8px 24px rgba(0, 0, 0, 0.4);
  --shadow-hover: 0 12px 32px rgba(124, 92, 255, 0.25);
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html, body {
  background: var(--bg-primary);
  color: var(--text-primary);
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  min-height: 100vh;
  line-height: 1.6;
}

body {
  background:
    radial-gradient(ellipse at top, rgba(124, 92, 255, 0.08), transparent 50%),
    radial-gradient(ellipse at bottom, rgba(96, 165, 250, 0.05), transparent 50%),
    var(--bg-primary);
}

/* === TOPBAR === */
.topbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1rem 2rem;
  background: rgba(19, 24, 41, 0.85);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 100;
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-weight: 700;
  font-size: 1.15rem;
}

.brand .logo {
  font-size: 1.8rem;
  filter: drop-shadow(0 0 8px var(--accent-glow));
}

.stats {
  display: flex;
  gap: 1rem;
}

.stat {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 0.4rem 0.9rem;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 8px;
  min-width: 64px;
}

.stat-label {
  font-size: 0.7rem;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.stat-value {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--text-primary);
}

/* === MAIN === */
main {
  max-width: 1200px;
  margin: 0 auto;
  padding: 2rem;
}

.view {
  animation: fadeIn 0.3s ease-out;
}

.view.hidden {
  display: none;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}

h1 {
  font-size: 2.2rem;
  font-weight: 800;
  margin-bottom: 0.5rem;
  background: linear-gradient(135deg, var(--text-primary), var(--accent));
  background-clip: text;
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

h2 {
  font-size: 1.5rem;
  font-weight: 700;
}

.lead {
  color: var(--text-secondary);
  margin-bottom: 2rem;
}

/* === DECK GRID === */
.deck-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1.25rem;
  margin-top: 1.5rem;
}

.deck-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 1.5rem;
  cursor: pointer;
  transition: all 0.2s ease;
  position: relative;
  overflow: hidden;
}

.deck-card::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 3px;
  background: linear-gradient(90deg, var(--accent), var(--blue));
  opacity: 0;
  transition: opacity 0.2s ease;
}

.deck-card:hover {
  background: var(--bg-card-hover);
  border-color: var(--border-hover);
  transform: translateY(-2px);
  box-shadow: var(--shadow-hover);
}

.deck-card:hover::before {
  opacity: 1;
}

.deck-icon {
  font-size: 2.4rem;
  margin-bottom: 0.5rem;
  filter: drop-shadow(0 4px 8px rgba(0, 0, 0, 0.3));
}

.deck-name {
  font-size: 1.15rem;
  font-weight: 700;
  margin-bottom: 0.25rem;
}

.deck-meta {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
  margin-top: 0.75rem;
}

.deck-tag {
  background: rgba(124, 92, 255, 0.15);
  color: var(--accent);
  padding: 0.15rem 0.6rem;
  border-radius: 6px;
  font-size: 0.75rem;
  font-weight: 500;
}

.deck-stats {
  margin-top: 1rem;
  display: flex;
  justify-content: space-between;
  font-size: 0.85rem;
  color: var(--text-secondary);
}

.deck-stats strong {
  color: var(--text-primary);
  font-weight: 600;
}

.empty {
  grid-column: 1/-1;
  text-align: center;
  padding: 3rem;
  color: var(--text-muted);
}

/* === STUDY VIEW === */
.study-header {
  display: flex;
  align-items: center;
  gap: 1rem;
  margin-bottom: 1rem;
}

.study-header h2 {
  flex: 1;
}

.progress-info {
  color: var(--text-secondary);
  font-size: 0.9rem;
  display: flex;
  gap: 0.5rem;
  align-items: center;
}

.progress-bar {
  height: 6px;
  background: var(--bg-card);
  border-radius: 3px;
  overflow: hidden;
  margin-bottom: 1.5rem;
}

.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent), var(--gold));
  transition: width 0.3s ease;
  width: 0%;
}

.card-area {
  display: flex;
  justify-content: center;
  perspective: 1200px;
  margin: 2rem 0;
}

.card {
  width: 100%;
  max-width: 640px;
  min-height: 320px;
  position: relative;
  cursor: pointer;
  transform-style: preserve-3d;
  transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
}

.card.flipped {
  transform: rotateY(180deg);
}

.card-inner {
  position: relative;
  width: 100%;
  height: 100%;
  min-height: inherit;
}

.card-face {
  position: absolute;
  inset: 0;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 18px;
  padding: 2rem;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  text-align: center;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  box-shadow: var(--shadow-card);
}

.card-back {
  transform: rotateY(180deg);
  background: linear-gradient(180deg, var(--bg-card), rgba(124, 92, 255, 0.08));
  border-color: var(--accent);
}

.card-label {
  position: absolute;
  top: 1rem;
  left: 1rem;
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-muted);
  font-weight: 600;
}

.card-content {
  font-size: 1.4rem;
  line-height: 1.6;
  max-width: 90%;
}

.card-source {
  position: absolute;
  bottom: 1rem;
  font-size: 0.8rem;
  color: var(--text-muted);
}

/* === CONTROLS === */
.controls {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1rem;
}

.btn-primary, .btn-ghost, .btn-rating {
  font-family: inherit;
  font-size: 1rem;
  font-weight: 600;
  padding: 0.75rem 1.5rem;
  border-radius: 10px;
  cursor: pointer;
  border: none;
  transition: all 0.15s ease;
}

.btn-primary {
  background: linear-gradient(135deg, var(--accent), #6047d1);
  color: white;
  box-shadow: 0 4px 14px var(--accent-glow);
}

.btn-primary:hover {
  transform: translateY(-1px);
  box-shadow: 0 6px 18px var(--accent-glow);
}

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

.btn-ghost:hover {
  background: var(--bg-card);
  color: var(--text-primary);
}

.rating {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0.5rem;
  width: 100%;
  max-width: 640px;
}

.rating.hidden {
  display: none;
}

.btn-rating {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 0.8rem 0.5rem;
  background: var(--bg-card);
  border: 1px solid var(--border);
  color: var(--text-primary);
}

.btn-rating:hover {
  background: var(--bg-card-hover);
  transform: translateY(-1px);
}

.btn-again { border-bottom: 3px solid var(--red); }
.btn-hard  { border-bottom: 3px solid var(--orange); }
.btn-good  { border-bottom: 3px solid var(--green); }
.btn-easy  { border-bottom: 3px solid var(--blue); }

.btn-rating:hover.btn-again { box-shadow: 0 4px 12px rgba(248, 113, 113, 0.3); }
.btn-rating:hover.btn-hard  { box-shadow: 0 4px 12px rgba(251, 146, 60, 0.3); }
.btn-rating:hover.btn-good  { box-shadow: 0 4px 12px rgba(74, 222, 128, 0.3); }
.btn-rating:hover.btn-easy  { box-shadow: 0 4px 12px rgba(96, 165, 250, 0.3); }

.rating-time {
  font-size: 0.75rem;
  color: var(--text-muted);
  margin-top: 0.2rem;
}

/* === VICTORY === */
.victory {
  text-align: center;
  padding: 3rem 1rem;
  max-width: 600px;
  margin: 0 auto;
}

.victory-icon {
  font-size: 5rem;
  margin-bottom: 1rem;
  filter: drop-shadow(0 0 20px var(--gold-glow));
  animation: bounceIn 0.6s cubic-bezier(0.34, 1.56, 0.64, 1);
}

@keyframes bounceIn {
  0% { transform: scale(0); }
  60% { transform: scale(1.15); }
  100% { transform: scale(1); }
}

.xp-gain {
  font-size: 2.2rem;
  font-weight: 800;
  color: var(--gold);
  margin: 1rem 0;
  text-shadow: 0 0 16px var(--gold-glow);
  animation: pulse 1.5s ease-in-out infinite;
}

.xp-gain.hidden {
  display: none;
}

@keyframes pulse {
  0%, 100% { transform: scale(1); }
  50% { transform: scale(1.05); }
}

.badges {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
  justify-content: center;
  margin: 1.5rem 0;
}

.badge {
  background: var(--bg-card);
  border: 1px solid var(--gold);
  color: var(--gold);
  padding: 0.5rem 1rem;
  border-radius: 999px;
  font-size: 0.85rem;
  font-weight: 600;
  box-shadow: 0 0 12px var(--gold-glow);
}

.done-actions {
  display: flex;
  gap: 1rem;
  justify-content: center;
  margin-top: 2rem;
}

/* === FOOTER === */
footer {
  text-align: center;
  padding: 2rem;
  color: var(--text-muted);
  font-size: 0.85rem;
  border-top: 1px solid var(--border);
  margin-top: 4rem;
}

footer a {
  color: var(--accent);
  text-decoration: none;
}

footer .version {
  margin-left: 1rem;
  font-family: monospace;
}

/* === MOBILE === */
@media (max-width: 640px) {
  .topbar { padding: 0.75rem 1rem; flex-direction: column; gap: 0.5rem; }
  main { padding: 1rem; }
  h1 { font-size: 1.6rem; }
  .card-content { font-size: 1.15rem; }
  .rating { grid-template-columns: repeat(2, 1fr); }
}