/* ==========================================================================
   MID-SEM MASTER VAULT — ACTIVE RECALL FLASHCARDS & SRS (M1)
   Ultra-polished 3D flip card engine, spaced repetition UI, theme variables
   ========================================================================== */

/* -------------------------------------------------------------
   MODAL CONTAINER & BACKDROP
   ------------------------------------------------------------- */
.flashcards-backdrop {
  position: fixed;
  inset: 0;
  background: rgba(8, 12, 20, 0.65);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  z-index: 9999;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1rem;
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
  transition: opacity 0.3s cubic-bezier(0.16, 1, 0.3, 1),
              visibility 0.3s cubic-bezier(0.16, 1, 0.3, 1);
}

.flashcards-backdrop.open {
  opacity: 1;
  visibility: visible;
  pointer-events: auto;
}

.flashcards-modal {
  background: var(--bg-card);
  border: 1px solid var(--border-card);
  border-radius: var(--radius-lg, 18px);
  box-shadow: var(--shadow-modal);
  width: 100%;
  max-width: 820px;
  max-height: 94vh;
  display: flex;
  flex-direction: column;
  overflow: hidden;
  position: relative;
  transform: scale(0.96) translateY(12px);
  transition: transform 0.3s cubic-bezier(0.16, 1, 0.3, 1);
}

.flashcards-backdrop.open .flashcards-modal {
  transform: scale(1) translateY(0);
}

/* -------------------------------------------------------------
   MODAL HEADER & TOOLBAR
   ------------------------------------------------------------- */
.flashcards-header {
  padding: 1rem 1.5rem;
  background: var(--bg-glass);
  border-bottom: 1px solid var(--border-card);
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  flex-shrink: 0;
}

.flashcards-header-top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.flashcards-title-group {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  flex-wrap: wrap;
}

.flashcards-title {
  font-family: var(--font-main);
  font-size: 1.15rem;
  font-weight: 800;
  color: var(--text-title);
  margin: 0;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.flashcards-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  padding: 0.2rem 0.6rem;
  border-radius: var(--radius-pill);
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.flashcards-badge.cn {
  background: var(--cn-bg);
  color: var(--cn-color);
  border: 1px solid var(--cn-border);
}

.flashcards-badge.daa {
  background: var(--daa-bg);
  color: var(--daa-color);
  border: 1px solid var(--daa-border);
}

.flashcards-badge.dmdw {
  background: var(--dmdw-bg);
  color: var(--dmdw-color);
  border: 1px solid var(--dmdw-border);
}

.flashcards-badge.hpc {
  background: var(--hpc-bg);
  color: var(--hpc-color);
  border: 1px solid var(--hpc-border);
}

.flashcards-badge.all {
  background: var(--accent-badge);
  color: var(--accent-primary);
  border: 1px solid var(--border-glass);
}

.flashcards-header-actions {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

/* -------------------------------------------------------------
   FILTER CHIPS & NAVIGATION
   ------------------------------------------------------------- */
.flashcards-filters {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
  flex-wrap: wrap;
}

.flashcards-filter-group {
  display: flex;
  align-items: center;
  gap: 0.35rem;
  overflow-x: auto;
  padding-bottom: 2px;
  scrollbar-width: none;
}

.flashcards-filter-group::-webkit-scrollbar {
  display: none;
}

.fc-chip {
  padding: 0.3rem 0.7rem;
  border-radius: var(--radius-pill);
  font-size: 0.78rem;
  font-weight: 600;
  background: var(--bg-input);
  color: var(--text-muted);
  border: 1px solid transparent;
  cursor: pointer;
  white-space: nowrap;
  transition: all 0.15s ease;
}

.fc-chip:hover {
  color: var(--text-title);
  border-color: var(--border-card-hover);
}

.fc-chip.active {
  background: var(--accent-primary);
  color: #ffffff;
  border-color: var(--accent-primary);
  box-shadow: 0 2px 6px var(--accent-glow);
}

.fc-chip.active-cn {
  background: var(--cn-color);
  color: #ffffff;
  border-color: var(--cn-color);
}
.fc-chip.active-daa {
  background: var(--daa-color);
  color: #ffffff;
  border-color: var(--daa-color);
}
.fc-chip.active-dmdw {
  background: var(--dmdw-color);
  color: #ffffff;
  border-color: var(--dmdw-color);
}
.fc-chip.active-hpc {
  background: var(--hpc-color);
  color: #ffffff;
  border-color: var(--hpc-color);
}

/* -------------------------------------------------------------
   PROGRESS TRACKER & SRS STATS BAR
   ------------------------------------------------------------- */
.flashcards-progress-bar-wrap {
  position: relative;
  width: 100%;
  height: 4px;
  background: var(--bg-input);
  overflow: hidden;
}

.flashcards-progress-fill {
  height: 100%;
  background: var(--accent-primary);
  width: 0%;
  transition: width 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.flashcards-stats-strip {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.4rem 1.5rem;
  background: var(--bg-page);
  border-bottom: 1px solid var(--border-card);
  font-size: 0.75rem;
  color: var(--text-muted);
  flex-shrink: 0;
}

.stats-counter-group {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.stat-pill {
  display: inline-flex;
  align-items: center;
  gap: 0.25rem;
  font-weight: 600;
}

.stat-pill.easy { color: #10b981; }
.stat-pill.review { color: #f59e0b; }
.stat-pill.hard { color: #ef4444; }

/* -------------------------------------------------------------
   CARD SCENE & 3D PERSPECTIVE CONTAINER
   ------------------------------------------------------------- */
.flashcards-body {
  padding: 1.5rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  flex: 1;
  overflow-y: auto;
  perspective: 1200px;
  min-height: 380px;
}

.card-scene {
  width: 100%;
  max-width: 680px;
  min-height: 340px;
  position: relative;
  perspective: 1200px;
  cursor: pointer;
  user-select: none;
  -webkit-user-select: none;
}

.card-flipper {
  width: 100%;
  min-height: 340px;
  position: relative;
  transform-style: preserve-3d;
  transition: transform 0.5s cubic-bezier(0.34, 1.35, 0.64, 1);
  border-radius: var(--radius-lg, 18px);
}

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

.card-face {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  border-radius: var(--radius-lg, 18px);
  background: var(--bg-card);
  border: 2px solid var(--border-card);
  box-shadow: var(--shadow-card);
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  padding: 1.5rem 1.75rem;
  overflow-y: auto;
  transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

.card-face:hover {
  border-color: var(--border-card-hover);
  box-shadow: var(--shadow-hover);
}

.card-face.card-front {
  transform: rotateY(0deg);
}

.card-face.card-back {
  transform: rotateY(180deg);
  background: var(--bg-card-hover, var(--bg-card));
  border-color: var(--accent-glow);
}

/* -------------------------------------------------------------
   CARD CONTENT LAYOUT
   ------------------------------------------------------------- */
.card-top-meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
  margin-bottom: 1rem;
}

.card-topic-breadcrumbs {
  font-size: 0.78rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-muted);
  display: flex;
  align-items: center;
  gap: 0.4rem;
}

.card-category-tag {
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
  font-size: 0.72rem;
  font-weight: 700;
  padding: 0.15rem 0.55rem;
  border-radius: var(--radius-pill);
  background: var(--bg-input);
  color: var(--text-body);
}

.card-difficulty-tag {
  font-size: 0.7rem;
  font-weight: 700;
  padding: 0.15rem 0.5rem;
  border-radius: var(--radius-pill);
}

.difficulty-easy { background: rgba(16, 185, 129, 0.12); color: #059669; }
.difficulty-medium { background: rgba(245, 158, 11, 0.12); color: #d97706; }
.difficulty-hard { background: rgba(239, 68, 68, 0.12); color: #dc2626; }

.card-center-prompt {
  flex: 1;
  display: flex;
  flex-direction: column;
  justify-content: center;
  text-align: center;
  padding: 1rem 0;
}

.card-prompt-text {
  font-family: var(--font-main);
  font-size: 1.25rem;
  font-weight: 700;
  line-height: 1.45;
  color: var(--text-title);
  margin-bottom: 0.75rem;
}

.card-context-note {
  font-size: 0.85rem;
  color: var(--text-muted);
  line-height: 1.4;
}

.card-bottom-hint {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.4rem;
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--text-subtle);
  padding-top: 0.75rem;
  border-top: 1px dashed var(--border-card);
}

/* Card Back Styles */
.card-answer-text {
  font-size: 1rem;
  line-height: 1.6;
  color: var(--text-title);
  margin-bottom: 1rem;
  white-space: pre-line;
}

.card-formula-box {
  background: var(--bg-input);
  border: 1px solid var(--border-card);
  border-radius: var(--radius-sm);
  padding: 0.75rem 1rem;
  font-family: var(--font-code);
  font-size: 0.9rem;
  color: var(--accent-primary);
  margin: 0.75rem 0;
  overflow-x: auto;
}

.card-callout {
  border-radius: var(--radius-sm);
  padding: 0.6rem 0.85rem;
  margin: 0.5rem 0;
  font-size: 0.82rem;
  line-height: 1.4;
  display: flex;
  align-items: flex-start;
  gap: 0.5rem;
}

.card-callout.memory-hook {
  background: rgba(124, 58, 237, 0.08);
  border-left: 3px solid #7c3aed;
  color: var(--text-body);
}

.card-callout.pyq-ref {
  background: rgba(2, 132, 199, 0.08);
  border-left: 3px solid #0284c7;
  color: var(--text-body);
}

.card-callout.takeaway {
  background: rgba(245, 158, 11, 0.08);
  border-left: 3px solid #f59e0b;
  color: var(--text-body);
}

/* -------------------------------------------------------------
   CARD CONTROLS & RATING DOCK
   ------------------------------------------------------------- */
.flashcards-footer {
  padding: 1rem 1.5rem;
  background: var(--bg-glass);
  border-top: 1px solid var(--border-card);
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  flex-shrink: 0;
}

.flashcards-rating-row {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0.75rem;
}

.fc-rate-btn {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 0.2rem;
  padding: 0.6rem 0.5rem;
  border-radius: var(--radius-md);
  border: 1px solid var(--border-card);
  background: var(--bg-card);
  color: var(--text-title);
  font-family: var(--font-main);
  font-weight: 700;
  font-size: 0.85rem;
  cursor: pointer;
  transition: all 0.2s cubic-bezier(0.16, 1, 0.3, 1);
}

.fc-rate-btn .rate-sub {
  font-size: 0.68rem;
  font-weight: 500;
  color: var(--text-muted);
}

.fc-rate-btn.rate-hard:hover {
  background: #fef2f2;
  border-color: #f87171;
  color: #dc2626;
  transform: translateY(-2px);
  box-shadow: 0 4px 10px rgba(239, 68, 68, 0.15);
}

.fc-rate-btn.rate-review:hover {
  background: #fffbeb;
  border-color: #fbbf24;
  color: #d97706;
  transform: translateY(-2px);
  box-shadow: 0 4px 10px rgba(245, 158, 11, 0.15);
}

.fc-rate-btn.rate-easy:hover {
  background: #f0fdf4;
  border-color: #4ade80;
  color: #16a34a;
  transform: translateY(-2px);
  box-shadow: 0 4px 10px rgba(16, 185, 129, 0.15);
}

[data-theme="dark"] .fc-rate-btn.rate-hard:hover {
  background: rgba(239, 68, 68, 0.15);
  border-color: #ef4444;
  color: #f87171;
}

[data-theme="dark"] .fc-rate-btn.rate-review:hover {
  background: rgba(245, 158, 11, 0.15);
  border-color: #f59e0b;
  color: #fbbf24;
}

[data-theme="dark"] .fc-rate-btn.rate-easy:hover {
  background: rgba(16, 185, 129, 0.15);
  border-color: #10b981;
  color: #4ade80;
}

[data-theme="sepia"] .fc-rate-btn.rate-hard:hover {
  background: #fae8e4;
  border-color: #e07262;
  color: #a82e1e;
}

[data-theme="sepia"] .fc-rate-btn.rate-review:hover {
  background: #fcf1d9;
  border-color: #d69e2e;
  color: #8c5b00;
}

[data-theme="sepia"] .fc-rate-btn.rate-easy:hover {
  background: #e6f4ea;
  border-color: #68b87d;
  color: #276738;
}

.flashcards-nav-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
}

.flashcards-shortcuts-bar {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.75rem;
  font-size: 0.72rem;
  color: var(--text-subtle);
  flex-wrap: wrap;
}

.fc-kbd {
  display: inline-block;
  padding: 0.1rem 0.35rem;
  font-family: var(--font-code);
  font-size: 0.68rem;
  font-weight: 700;
  color: var(--text-title);
  background: var(--bg-input);
  border: 1px solid var(--border-card);
  border-radius: var(--radius-xs);
  box-shadow: 0 1px 1px rgba(0, 0, 0, 0.1);
}

/* -------------------------------------------------------------
   EMPTY & COMPLETED STATE
   ------------------------------------------------------------- */
.flashcards-empty-state {
  text-align: center;
  padding: 3rem 1.5rem;
  max-width: 460px;
  margin: 0 auto;
}

.flashcards-empty-icon {
  font-size: 3rem;
  margin-bottom: 1rem;
}

.flashcards-empty-title {
  font-family: var(--font-main);
  font-size: 1.25rem;
  font-weight: 800;
  color: var(--text-title);
  margin-bottom: 0.5rem;
}

.flashcards-empty-desc {
  font-size: 0.88rem;
  color: var(--text-muted);
  line-height: 1.5;
  margin-bottom: 1.5rem;
}

/* -------------------------------------------------------------
   RESPONSIVE QUERIES
   ------------------------------------------------------------- */
@media (max-width: 640px) {
  .flashcards-modal {
    max-height: 100vh;
    height: 100%;
    border-radius: 0;
  }
  
  .card-face {
    padding: 1.25rem;
  }
  
  .card-prompt-text {
    font-size: 1.05rem;
  }
  
  .flashcards-shortcuts-bar {
    display: none;
  }
}