/* ══════════════════════════════════════════════════════
   Flashcards — Shared Styles
   ══════════════════════════════════════════════════════ */
:root {
  --bg: #08090e; --bg-raised: #0f1118; --bg-card: #151821;
  --border: rgba(255,255,255,0.06); --border-accent: rgba(108,140,255,0.25);
  --text: #e8eaf0; --text-secondary: #a0a8c0; --text-dim: #5e6580;
  --accent: #6c8cff; --accent-soft: rgba(108,140,255,0.1); --accent-glow: rgba(108,140,255,0.15);
  --green: #22d3a7; --green-soft: rgba(34,211,167,0.1); --green-border: rgba(34,211,167,0.25);
  --red: #f06070; --red-soft: rgba(240,96,112,0.1); --red-border: rgba(240,96,112,0.25);
  --yellow: #f0b040; --yellow-soft: rgba(240,176,64,0.1); --yellow-border: rgba(240,176,64,0.25);
  --purple: #a78bfa; --purple-soft: rgba(167,139,250,0.1);
  --font: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  --mono: 'JetBrains Mono', monospace;
  --radius: 16px; --radius-sm: 10px;
  --transition: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body { font-family: var(--font); background: var(--bg); color: var(--text); min-height: 100vh; overflow-x: hidden; }

/* Nav */
.nav-bar {
  position: sticky; top: 0; z-index: 100;
  display: flex; align-items: center; gap: 0.5rem;
  padding: 0 1.5rem; height: 56px;
  background: rgba(8,9,14,0.85); backdrop-filter: blur(20px) saturate(1.6);
  border-bottom: 1px solid var(--border);
}
.nav-bar a { color: var(--text-secondary); text-decoration: none; font-size: 0.82rem; font-weight: 600; padding: 0.4rem 0.75rem; border-radius: 8px; transition: all var(--transition); }
.nav-bar a:hover { color: var(--accent); background: var(--accent-soft); }
.nav-title { font-size: 1rem; font-weight: 800; background: linear-gradient(135deg, #e8eaf0 0%, var(--accent) 100%); -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text; }
.nav-spacer { flex: 1; }
#langToggle {
  background: transparent; border: 1px solid var(--border-accent); color: var(--accent);
  font-size: 0.78rem; font-weight: 700; padding: 0.32rem 0.85rem; border-radius: 20px;
  cursor: pointer; font-family: var(--font); transition: all var(--transition);
}
#langToggle:hover { background: var(--accent); color: #fff; }

/* Config panel */
.config-panel { max-width: 900px; margin: 0 auto; padding: 1.5rem 1.5rem 0; }
.config-toggle {
  display: flex; align-items: center; gap: 0.6rem; cursor: pointer;
  padding: 0.75rem 1rem; border-radius: var(--radius); margin-bottom: 0.75rem;
  background: var(--bg-raised); border: 1px solid var(--border); transition: all var(--transition); user-select: none;
}
.config-toggle:hover { border-color: var(--border-accent); }
.config-toggle .cfg-icon { font-size: 1.1rem; }
.config-toggle .cfg-label { font-size: 0.88rem; font-weight: 700; flex: 1; }
.config-toggle .cfg-summary { font-size: 0.78rem; color: var(--text-dim); font-weight: 500; }
.config-toggle .cfg-arrow { transition: transform var(--transition); color: var(--text-dim); font-size: 0.9rem; }
.config-toggle.open .cfg-arrow { transform: rotate(180deg); }
.config-body { display: none; animation: slideDown 0.3s ease-out; }
.config-body.show { display: block; }
@keyframes slideDown { from { opacity: 0; transform: translateY(-8px); } to { opacity: 1; transform: translateY(0); } }

.config-row { display: flex; gap: 1rem; padding-bottom: 1.25rem; flex-wrap: wrap; }
.cfg-card { background: var(--bg-raised); border: 1px solid var(--border); border-radius: var(--radius); padding: 1.15rem; flex: 1; min-width: 220px; }
.cfg-card h4 { font-size: 0.68rem; text-transform: uppercase; letter-spacing: 0.1em; color: var(--text-dim); margin-bottom: 0.75rem; font-weight: 700; }

.ch-chips { display: flex; flex-wrap: wrap; gap: 0.35rem; }
.ch-chip {
  padding: 0.35rem 0.65rem; border-radius: 8px; font-size: 0.76rem; font-weight: 600;
  border: 1px solid var(--border); background: transparent; color: var(--text-dim);
  cursor: pointer; transition: all var(--transition); font-family: var(--font); line-height: 1;
}
.ch-chip.active { background: var(--accent); color: #fff; border-color: var(--accent); box-shadow: 0 2px 12px rgba(108,140,255,0.25); }
.ch-chip:hover:not(.active) { border-color: var(--accent); color: var(--text-secondary); }
.ch-chip-action { padding: 0.3rem 0.55rem; border-radius: 6px; font-size: 0.68rem; font-weight: 700; border: 1px dashed var(--border); background: transparent; color: var(--text-dim); cursor: pointer; transition: all var(--transition); font-family: var(--font); text-transform: uppercase; letter-spacing: 0.06em; }
.ch-chip-action:hover { border-color: var(--accent); color: var(--accent); }

.toggle-row { display: flex; align-items: center; gap: 0.75rem; padding: 0.5rem 0; cursor: pointer; user-select: none; }
.toggle-row .toggle-label { font-size: 0.85rem; font-weight: 500; color: var(--text-secondary); flex: 1; }
.toggle-switch { width: 40px; height: 22px; border-radius: 11px; position: relative; background: rgba(255,255,255,0.08); border: 1px solid rgba(255,255,255,0.1); transition: all var(--transition); flex-shrink: 0; }
.toggle-switch::after { content: ""; position: absolute; top: 2px; left: 2px; width: 16px; height: 16px; border-radius: 50%; background: var(--text-dim); transition: all var(--transition); }
.toggle-row input { display: none; }
.toggle-row input:checked + .toggle-switch { background: var(--accent); border-color: var(--accent); }
.toggle-row input:checked + .toggle-switch::after { transform: translateX(18px); background: #fff; }

/* Stats */
.stats-row { display: grid; grid-template-columns: 1fr 1fr 1fr; gap: 0.75rem; margin-bottom: 0.75rem; }
.stat-card { background: var(--bg-raised); border: 1px solid var(--border); border-radius: var(--radius); padding: 0.85rem; text-align: center; position: relative; overflow: hidden; }
.stat-card::before { content: ""; position: absolute; top: 0; left: 0; right: 0; height: 2px; }
.stat-card.due-stat::before { background: linear-gradient(90deg, transparent, var(--yellow), transparent); }
.stat-card.new-stat::before { background: linear-gradient(90deg, transparent, var(--accent), transparent); }
.stat-card.total-stat::before { background: linear-gradient(90deg, transparent, var(--green), transparent); }
.stat-value { font-size: 1.6rem; font-weight: 800; font-family: var(--mono); line-height: 1.1; }
.stat-label { font-size: 0.68rem; color: var(--text-dim); margin-top: 0.2rem; text-transform: uppercase; letter-spacing: 0.06em; font-weight: 600; }

/* Buttons */
.btn { padding: 0.7rem 1.5rem; border-radius: var(--radius-sm); font-size: 0.88rem; font-weight: 700; border: none; cursor: pointer; font-family: var(--font); transition: all var(--transition); display: inline-flex; align-items: center; gap: 0.4rem; }
.btn-primary { background: linear-gradient(135deg, var(--accent) 0%, #5a7ae6 100%); color: #fff; box-shadow: 0 4px 20px rgba(108,140,255,0.3); }
.btn-primary:hover { box-shadow: 0 6px 28px rgba(108,140,255,0.45); transform: translateY(-1px); }
.btn-ghost { background: transparent; border: 1px solid var(--border); color: var(--text-secondary); }
.btn-ghost:hover { border-color: var(--accent); color: var(--accent); }
.action-row { display: flex; gap: 0.6rem; flex-wrap: wrap; margin-bottom: 1.5rem; }

/* ── FLASHCARD AREA ── */
.fc-wrapper { max-width: 700px; margin: 0 auto; padding: 0 1.5rem 3rem; min-height: 60vh; }

.empty-hero { text-align: center; padding: clamp(3rem, 10vh, 6rem) 1.5rem; position: relative; }
.empty-hero::before { content: ""; position: absolute; top: 20%; left: 50%; transform: translateX(-50%); width: 400px; height: 300px; background: radial-gradient(ellipse, rgba(108,140,255,0.08), transparent 70%); pointer-events: none; }
.empty-icon { font-size: 3.5rem; margin-bottom: 1.2rem; display: block; position: relative; }
.empty-hero h2 { font-size: clamp(1.5rem, 3vw, 2rem); font-weight: 800; position: relative; background: linear-gradient(135deg, #e8eaf0, var(--accent)); -webkit-background-clip: text; -webkit-text-fill-color: transparent; }
.empty-hero p { color: var(--text-dim); font-size: 1.02rem; line-height: 1.7; margin-top: 0.7rem; max-width: 480px; margin-left: auto; margin-right: auto; position: relative; }

/* Card */
.fc-card-container { perspective: 1200px; margin-bottom: 1rem; }
.fc-card {
  position: relative; min-height: 280px; border-radius: 24px; cursor: pointer;
  transform-style: preserve-3d; transition: transform 0.55s cubic-bezier(0.4, 0, 0.2, 1);
}
.fc-card.flipped { transform: rotateY(180deg); }
.fc-face {
  position: absolute; inset: 0; backface-visibility: hidden; -webkit-backface-visibility: hidden;
  border-radius: 24px; padding: clamp(1.5rem, 3vw, 2.25rem);
  display: flex; flex-direction: column;
  background: var(--bg-card); border: 1px solid var(--border);
  box-shadow: 0 8px 40px rgba(0,0,0,0.3);
  overflow: hidden;
}
.fc-face::before { content: ""; position: absolute; top: 0; left: 0; right: 0; height: 3px; }
.fc-front::before { background: linear-gradient(90deg, var(--accent), var(--purple)); opacity: 0.6; }
.fc-back { transform: rotateY(180deg); }
.fc-back::before { background: linear-gradient(90deg, var(--green), var(--accent)); opacity: 0.6; }

.fc-badge-row { display: flex; align-items: center; gap: 0.5rem; margin-bottom: 1rem; }
.fc-badge { font-family: var(--mono); font-size: 0.72rem; font-weight: 700; padding: 0.28rem 0.65rem; border-radius: 8px; }
.fc-badge.ch-badge { background: var(--accent-soft); color: var(--accent); }
.fc-badge.side-badge { background: var(--purple-soft); color: var(--purple); }
.fc-badge.ans-badge { background: var(--green-soft); color: var(--green); }

.fc-body { flex: 1; font-size: clamp(1.05rem, 2vw, 1.25rem); line-height: 1.6; font-weight: 500; display: flex; align-items: center; }
.fc-body-inner { width: 100%; }
.fc-tap-hint { margin-top: auto; padding-top: 1rem; font-size: 0.76rem; color: var(--text-dim); text-align: center; }

/* Rating */
.fc-rating { margin-bottom: 1rem; animation: fadeIn 0.3s ease-out; }
@keyframes fadeIn { from { opacity: 0; transform: translateY(6px); } to { opacity: 1; transform: translateY(0); } }
.fc-rate-label { font-size: 0.72rem; color: var(--text-dim); text-transform: uppercase; letter-spacing: 0.08em; font-weight: 700; margin-bottom: 0.65rem; text-align: center; }
.fc-rate-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 0.5rem; }
.fc-rate-btn {
  padding: 0.7rem 0.5rem; border-radius: var(--radius-sm); font-size: 0.85rem; font-weight: 700;
  border: 1px solid; cursor: pointer; font-family: var(--font); transition: all var(--transition);
  display: flex; flex-direction: column; align-items: center; gap: 0.15rem;
}
.fc-rate-btn .rate-sub { font-size: 0.62rem; font-weight: 500; opacity: 0.7; }
.fc-rate-btn.r-again { background: var(--red-soft); color: var(--red); border-color: var(--red-border); }
.fc-rate-btn.r-hard { background: var(--yellow-soft); color: var(--yellow); border-color: var(--yellow-border); }
.fc-rate-btn.r-good { background: var(--green-soft); color: var(--green); border-color: var(--green-border); }
.fc-rate-btn.r-easy { background: var(--accent-soft); color: var(--accent); border-color: var(--border-accent); }
.fc-rate-btn:hover { filter: brightness(1.15); transform: translateY(-1px); }
@media (max-width: 480px) { .fc-rate-grid { grid-template-columns: repeat(2, 1fr); } }

/* Session nav */
.fc-session-bar {
  display: flex; align-items: center; justify-content: space-between;
  padding: 0.6rem 0.85rem; background: var(--bg-raised); border: 1px solid var(--border);
  border-radius: var(--radius-sm);
}
.fc-session-bar .nav-btn { display: inline-flex; align-items: center; gap: 0.3rem; padding: 0.45rem 0.9rem; border-radius: 8px; font-size: 0.82rem; font-weight: 600; border: 1px solid var(--border); background: transparent; color: var(--text-secondary); cursor: pointer; font-family: var(--font); transition: all var(--transition); }
.fc-session-bar .nav-btn:hover { border-color: var(--accent); color: var(--accent); }
.fc-counter { font-family: var(--mono); font-size: 0.85rem; font-weight: 700; color: var(--text); }

.fc-progress-dots { display: flex; gap: 3px; align-items: center; justify-content: center; margin-bottom: 0.75rem; flex-wrap: wrap; }
.fc-dot { width: 7px; height: 7px; border-radius: 50%; background: rgba(255,255,255,0.08); transition: all var(--transition); }
.fc-dot.current { background: var(--accent); box-shadow: 0 0 8px rgba(108,140,255,0.5); transform: scale(1.4); }
.fc-dot.rated { background: var(--green); }

/* Done */
.fc-done { text-align: center; padding: clamp(3rem, 8vh, 5rem) 1.5rem; }
.fc-done h2 { font-size: 1.8rem; font-weight: 800; color: var(--green); margin-bottom: 0.5rem; }
.fc-done p { color: var(--text-dim); font-size: 1rem; line-height: 1.6; margin-bottom: 1.5rem; }

.kbd-hints { display: flex; gap: 1rem; justify-content: center; margin-top: 1rem; flex-wrap: wrap; }
.kbd { font-family: var(--mono); font-size: 0.68rem; color: var(--text-dim); display: flex; align-items: center; gap: 0.3rem; }
.kbd kbd { display: inline-block; padding: 0.15rem 0.45rem; border-radius: 4px; background: rgba(255,255,255,0.06); border: 1px solid var(--border); font-family: var(--mono); font-size: 0.68rem; }

@media (max-width: 768px) {
  .nav-bar { padding: 0 1rem; }
  .config-panel, .fc-wrapper { padding-left: 1rem; padding-right: 1rem; }
  .stat-value { font-size: 1.3rem; }
  .fc-face { padding: 1.25rem; }
  .kbd-hints { display: none; }
}