:root {
  --bg: #faf8f4;
  --surface: #ffffff;
  --surface-muted: #f3f0ea;
  --text: #1a1714;
  --text-muted: #4a4540;
  --text-faint: #8a8480;
  --border: #eae5da;
  --primary: #1a1714;
  --primary-text: #faf8f4;
  --primary-hover: #322c26;
  --success: #3f7d52;
  --danger: #b3492f;
  --accent-bg: #f3f0ea;
  --shadow: 0 1px 2px rgba(26,23,20,0.04), 0 8px 24px rgba(26,23,20,0.05);
  --radius: 16px;

  /* single brand accent, used sparingly for pops of emphasis */
  --accent: #b5622a;
  --accent-soft: #f1ded0;

  /* mastery states — used consistently across deck cards, study & manage views */
  --known: #3f7d52;
  --known-soft: #dcead9;
  --learning: #c98a2e;
  --learning-soft: #f5e6c9;
  --new: #9a948c;
  --new-soft: #ecebe6;

  --font-sans: "Figtree", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  --font-serif: "Instrument Serif", Georgia, serif;
  --font-mono: "DM Mono", "SFMono-Regular", Consolas, monospace;
}

[data-theme="dark"] {
  --bg: #18140f;
  --surface: #211d19;
  --surface-muted: #28221c;
  --text: #f5efe4;
  --text-muted: #c9c2b8;
  --text-faint: #8a8074;
  --border: #37302a;
  --primary: #f5efe4;
  --primary-text: #18140f;
  --primary-hover: #ffffff;
  --success: #7fbf94;
  --danger: #e08066;
  --accent-bg: #28221c;
  --shadow: 0 1px 2px rgba(0,0,0,0.2), 0 8px 24px rgba(0,0,0,0.3);

  --accent: #e08a4f;
  --accent-soft: #3a2a1c;

  --known: #7fbf94;
  --known-soft: #22362a;
  --learning: #e0b464;
  --learning-soft: #3a301c;
  --new: #8a8074;
  --new-soft: #2a2620;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: var(--font-sans);
  background: var(--bg);
  color: var(--text);
  transition: background 0.2s, color 0.2s;
}

.app-header {
  background: color-mix(in srgb, var(--bg) 92%, transparent);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 10;
}

.header-inner {
  max-width: 960px;
  margin: 0 auto;
  padding: 16px 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 10px;
}

.logo {
  margin: 0;
  font-family: var(--font-serif);
  font-weight: 400;
  font-size: 1.65rem;
  letter-spacing: -0.01em;
}
.logo em { font-style: italic; color: var(--text-faint); }

.header-actions { display: flex; gap: 8px; flex-wrap: wrap; }

.app-main {
  max-width: 960px;
  margin: 0 auto;
  padding: 32px 24px 60px;
}

.btn {
  border: 1px solid transparent;
  border-radius: 100px;
  padding: 10px 20px;
  font-size: 0.9rem;
  font-family: var(--font-sans);
  cursor: pointer;
  font-weight: 600;
  transition: background 0.15s, border-color 0.15s, color 0.15s, transform 0.05s;
}
.btn:active { transform: scale(0.97); }
.btn-sm { padding: 6px 14px; font-size: 0.8rem; }

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

.btn-ghost { background: transparent; color: var(--text); border-color: var(--border); }
.btn-ghost:hover { background: var(--accent-bg); }

.btn-learning { background: var(--learning-soft); color: var(--learning); border-color: transparent; }
.btn-learning:hover { background: var(--learning); color: var(--primary-text); }

.btn-known { background: var(--known); color: var(--primary-text); }
.btn-known:hover { filter: brightness(0.92); }

.btn-icon { padding: 8px 12px; border-radius: 100px; }

.toolbar { margin-bottom: 18px; }

.search-input {
  width: 100%;
  padding: 12px 16px;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: var(--surface-muted);
  color: var(--text);
  font-size: 0.95rem;
  font-family: var(--font-sans);
  margin-bottom: 10px;
}
.search-input:focus { outline: 2px solid var(--text); outline-offset: 1px; }

.deck-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 16px;
}

.deck-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px;
  box-shadow: var(--shadow);
  display: flex;
  flex-direction: column;
  gap: 10px;
  position: relative;
}

.deck-card-top { display: flex; justify-content: space-between; align-items: baseline; gap: 8px; }
.deck-card-title { margin: 0; font-family: var(--font-serif); font-weight: 400; font-size: 1.35rem; }
.deck-card-count {
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--text-faint);
  white-space: nowrap;
}
.deck-card-desc { margin: 0; color: var(--text-muted); font-size: 0.85rem; min-height: 1.2em; }

.mastered-badge {
  position: absolute;
  top: 16px;
  right: 16px;
  background: var(--accent-soft);
  color: var(--accent);
  font-family: var(--font-mono);
  font-size: 0.6rem;
  letter-spacing: 0.08em;
  padding: 3px 9px;
  border-radius: 999px;
}
.mastered-badge[hidden] { display: none; }

.progress-bar, .progress-track {
  background: var(--new-soft);
  border-radius: 999px;
  height: 6px;
  overflow: hidden;
  display: flex;
}
.progress-fill {
  background: var(--text);
  height: 100%;
  width: 0%;
  transition: width 0.25s ease;
}
.progress-seg { height: 100%; width: 0%; transition: width 0.25s ease; }
.progress-seg.seg-known { background: var(--known); }
.progress-seg.seg-learning { background: var(--learning); }

.deck-card-stats {
  font-family: var(--font-mono);
  font-size: 0.65rem;
  letter-spacing: 0.03em;
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
}
.stat-dot { display: inline-block; width: 6px; height: 6px; border-radius: 999px; margin-right: 4px; vertical-align: middle; }
.stat-known { color: var(--known); }
.stat-known .stat-dot { background: var(--known); }
.stat-learning { color: var(--learning); }
.stat-learning .stat-dot { background: var(--learning); }
.stat-new { color: var(--text-faint); }
.stat-new .stat-dot { background: var(--new); }

.deck-card-actions { display: flex; gap: 6px; flex-wrap: wrap; margin-top: 4px; }

.empty-state { color: var(--text-muted); text-align: center; padding: 40px 10px; }

/* Study view */
.study-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 10px;
  margin-bottom: 14px;
}
.study-header h2 { margin: 0; font-family: var(--font-serif); font-weight: 400; font-size: 1.6rem; }
.study-controls { display: flex; align-items: center; gap: 12px; }
.shuffle-toggle {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  display: flex;
  align-items: center;
  gap: 6px;
  color: var(--text-faint);
}

.streak-pill {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  background: var(--accent-soft);
  color: var(--accent);
  font-family: var(--font-mono);
  font-size: 0.62rem;
  letter-spacing: 0.06em;
  padding: 5px 11px;
  border-radius: 999px;
}
.streak-pill[hidden] { display: none; }

.study-progress {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 20px;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.04em;
  color: var(--known);
}
.study-progress .progress-bar, .study-progress .progress-track { flex: 1; }
.study-position { color: var(--text-faint); }

.card-stage { display: flex; justify-content: center; margin-bottom: 20px; perspective: 1200px; }

.flashcard {
  width: 100%;
  max-width: 520px;
  min-height: 280px;
  cursor: pointer;
  outline: none;
}

.flashcard-inner {
  width: 100%;
  min-height: inherit;
  display: grid;
  transition: transform 0.5s cubic-bezier(.4,.2,.2,1);
  transform-style: preserve-3d;
}
.flashcard.flipped .flashcard-inner { transform: rotateY(180deg); }

.flashcard-face {
  grid-row: 1;
  grid-column: 1;
  position: relative;
  min-height: inherit;
  backface-visibility: hidden;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background: var(--surface);
  box-shadow: var(--shadow);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 28px 24px 46px;
  gap: 14px;
}
.flashcard-back { transform: rotateY(180deg); background: var(--surface-muted); }

.face-label {
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-faint);
  font-weight: 500;
}
.face-text { font-family: var(--font-serif); font-size: 1.7rem; font-weight: 400; margin: 0; word-break: break-word; }
.face-text.code-text {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  font-weight: 400;
  text-align: left;
  align-self: stretch;
  white-space: pre-wrap;
  max-height: 190px;
  overflow-y: auto;
}
.tap-hint {
  font-family: var(--font-mono);
  font-size: 0.65rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--text-faint);
  position: absolute;
  bottom: 14px;
}

/* Non-flip interactive card types (mcq, true-false, fill-blank) */
.card-mount { width: 100%; display: flex; justify-content: center; }

.choice-card, .fillblank-card {
  width: 100%;
  max-width: 520px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 28px;
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.choice-question, .fillblank-question {
  font-family: var(--font-serif);
  font-size: 1.5rem;
  font-weight: 400;
  margin: 0;
  white-space: pre-wrap;
}

.choice-options { display: flex; flex-direction: column; gap: 8px; }

.choice-option {
  text-align: left;
  padding: 12px 16px;
  border-radius: 12px;
  border: 1px dashed var(--border);
  background: var(--surface-muted);
  color: var(--text);
  font-size: 0.92rem;
  font-family: var(--font-sans);
  cursor: pointer;
}
.choice-option:hover:not(:disabled) { border-color: var(--text-faint); }
.choice-option:disabled { cursor: default; }
.choice-option.choice-correct { border-style: solid; border-color: var(--success); background: var(--success); color: var(--primary-text); }
.choice-option.choice-incorrect { border-style: solid; border-color: var(--danger); background: var(--danger); color: var(--primary-text); }

.choice-explanation {
  margin: 0;
  padding-top: 10px;
  border-top: 1px solid var(--border);
  color: var(--text-muted);
  font-size: 0.88rem;
}

.fillblank-input-row { display: flex; gap: 8px; }
.fillblank-input { margin-bottom: 0; flex: 1; }

.fillblank-feedback { margin: 0; font-weight: 600; font-size: 0.92rem; }
.fillblank-feedback.feedback-correct { color: var(--success); }
.fillblank-feedback.feedback-incorrect { color: var(--danger); }

.study-nav {
  display: flex;
  justify-content: center;
  gap: 10px;
  flex-wrap: wrap;
  margin-bottom: 10px;
}

.keyboard-hint {
  text-align: center;
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.02em;
  color: var(--text-faint);
}

@media (max-width: 480px) {
  .study-nav .btn { flex: 1 1 40%; }
}