/* ============================================
   SAT Vocabulary Trainer — Design System
   Based on Apple HIG / astroblog palette
   ============================================ */

/* ----- Light Mode (Default) ----- */
:root {
  --bg:         #f2f2f4;
  --card:       #ffffff;
  --bg3:        #e8e8ed;
  --glass:      rgba(242,242,244,0.8);
  --hairline:   rgba(0,0,0,0.06);
  --txt:        #1d1d1f;
  --txt2:       #48484d;
  --txt3:       #86868b;
  --accent:     #0071e3;
  --accent-hover: #0077ed;
  --accent-bg:  rgba(0,113,227,0.08);
  --success:    #30b158;
  --success-bg: rgba(48,177,88,0.08);
  --danger:     #e0303f;
  --danger-bg:  rgba(224,48,63,0.08);
  --warning:    #ff9f0a;
  --warning-bg: rgba(255,159,10,0.08);
  --card-shadow:       0 1px 3px rgba(0,0,0,0.04), 0 4px 12px rgba(0,0,0,0.06), 0 8px 24px rgba(0,0,0,0.04);
  --card-shadow-hover: 0 8px 32px rgba(0,0,0,0.08), 0 16px 56px rgba(0,0,0,0.06);
  --radius:      22px;
  --radius-sm:   12px;
  --radius-xs:   8px;
  --font:        -apple-system, BlinkMacSystemFont, "SF Pro Display", "PingFang SC", "Helvetica Neue", sans-serif;
  --ease:        cubic-bezier(0.16, 1, 0.3, 1);
}

/* ----- Dark Mode (system preference, no manual override) ----- */
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg:         #0a0a0c;
    --card:       #1c1c1e;
    --bg3:        #2c2c2e;
    --glass:      rgba(10,10,12,0.8);
    --hairline:   rgba(255,255,255,0.06);
    --txt:        #f5f5f7;
    --txt2:       #98989d;
    --txt3:       #6e6e73;
    --accent:     #2997ff;
    --accent-hover: #40a9ff;
    --accent-bg:  rgba(41,151,255,0.12);
    --success:    #30d158;
    --success-bg: rgba(48,209,88,0.1);
    --danger:     #ff453a;
    --danger-bg:  rgba(255,69,58,0.1);
    --warning:    #ffd60a;
    --warning-bg: rgba(255,214,10,0.1);
    --card-shadow:       0 0 0 1px rgba(255,255,255,0.06), 0 4px 16px rgba(0,0,0,0.2);
    --card-shadow-hover: 0 0 0 1px rgba(255,255,255,0.1), 0 8px 32px rgba(0,0,0,0.3);
  }
}

/* ----- Dark Mode (manual override) ----- */
:root[data-theme="dark"] {
  --bg:         #0a0a0c;
  --card:       #1c1c1e;
  --bg3:        #2c2c2e;
  --glass:      rgba(10,10,12,0.8);
  --hairline:   rgba(255,255,255,0.06);
  --txt:        #f5f5f7;
  --txt2:       #98989d;
  --txt3:       #6e6e73;
  --accent:     #2997ff;
  --accent-hover: #40a9ff;
  --accent-bg:  rgba(41,151,255,0.12);
  --success:    #30d158;
  --success-bg: rgba(48,209,88,0.1);
  --danger:     #ff453a;
  --danger-bg:  rgba(255,69,58,0.1);
  --warning:    #ffd60a;
  --warning-bg: rgba(255,214,10,0.1);
  --card-shadow:       0 0 0 1px rgba(255,255,255,0.06), 0 4px 16px rgba(0,0,0,0.2);
  --card-shadow-hover: 0 0 0 1px rgba(255,255,255,0.1), 0 8px 32px rgba(0,0,0,0.3);
}

/* ----- Theme toggle button ----- */
.theme-toggle {
  width: 34px;
  height: 34px;
  border-radius: 50%;
  border: 1px solid var(--hairline);
  background: transparent;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--txt2);
  transition: all 0.25s var(--ease);
  flex-shrink: 0;
}
.theme-toggle:hover { background: var(--bg3); color: var(--txt); }
.theme-toggle svg { width: 16px; height: 16px; }
.theme-toggle .icon-sun  { display: none; }
.theme-toggle .icon-moon { display: block; }
:root[data-theme="dark"] .theme-toggle .icon-sun  { display: block; }
:root[data-theme="dark"] .theme-toggle .icon-moon { display: none; }
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) .theme-toggle .icon-sun  { display: block; }
  :root:not([data-theme="light"]) .theme-toggle .icon-moon { display: none; }
}

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

body {
  font-family: var(--font);
  font-size: 16px;
  font-weight: 400;
  line-height: 1.6;
  letter-spacing: -0.01em;
  color: var(--txt);
  background: var(--bg);
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

a { color: var(--accent); text-decoration: none; transition: color 0.2s var(--ease); }
a:hover { color: var(--accent-hover); }

/* ----- Header ----- */
.app-header {
  position: sticky;
  top: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 52px;
  padding: 0 48px;
  background: var(--glass);
  backdrop-filter: saturate(180%) blur(20px);
  -webkit-backdrop-filter: saturate(180%) blur(20px);
  border-bottom: 1px solid var(--hairline);
  gap: 24px;
}

.app-title {
  font-size: 1rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--txt);
  cursor: pointer;
  user-select: none;
  white-space: nowrap;
}

.header-nav {
  display: flex;
  gap: 2px;
}

.nav-link {
  padding: 6px 14px;
  border-radius: 6px;
  font-size: 0.8125rem;
  font-weight: 500;
  letter-spacing: -0.01em;
  color: var(--txt2);
  transition: all 0.2s var(--ease);
}

.nav-link:hover { color: var(--txt); background: var(--bg3); }
.nav-link.active { color: var(--accent); background: var(--accent-bg); }

/* ----- Main Content ----- */
#main-content {
  max-width: 1300px;
  margin: 0 auto;
  padding: 48px;
}

.loading {
  text-align: center;
  padding: 80px 20px;
  color: var(--txt3);
  font-size: 0.9375rem;
}

/* ----- Page Titles ----- */
.page-title {
  font-size: 2rem;
  font-weight: 700;
  letter-spacing: -0.04em;
  color: var(--txt);
}

.page-subtitle {
  font-size: 0.9375rem;
  color: var(--txt3);
  margin-top: 6px;
  letter-spacing: -0.01em;
}

.toolbar {
  display: flex;
  gap: 12px;
  margin: 32px 0;
  flex-wrap: wrap;
  align-items: center;
}

/* ----- Buttons ----- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  padding: 10px 20px;
  border: none;
  border-radius: 100px;
  font-family: var(--font);
  font-size: 0.875rem;
  font-weight: 500;
  letter-spacing: -0.01em;
  cursor: pointer;
  transition: all 0.25s var(--ease);
  white-space: nowrap;
  -webkit-font-smoothing: antialiased;
}

.btn:disabled { opacity: 0.4; cursor: not-allowed; pointer-events: none; }
.btn:active { transform: scale(0.97); }

.btn-primary {
  background: var(--accent);
  color: #fff;
}
.btn-primary:hover:not(:disabled) { background: var(--accent-hover); }

.btn-success {
  background: var(--success);
  color: #fff;
}
.btn-success:hover:not(:disabled) { filter: brightness(1.1); }

.btn-danger {
  background: var(--danger);
  color: #fff;
}
.btn-danger:hover:not(:disabled) { filter: brightness(1.1); }

.btn-outline {
  background: transparent;
  border: 1px solid var(--hairline);
  color: var(--txt2);
}
.btn-outline:hover:not(:disabled) {
  background: var(--bg3);
  color: var(--txt);
}

.btn-ghost {
  background: transparent;
  color: var(--txt2);
}
.btn-ghost:hover:not(:disabled) {
  background: var(--bg3);
  color: var(--txt);
}

.btn-sm { padding: 6px 14px; font-size: 0.8125rem; }
.btn-lg { padding: 14px 28px; font-size: 1rem; }
.btn-icon { width: 36px; height: 36px; padding: 0; border-radius: 50%; }

/* ----- Set Grid (Home) ----- */
.set-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 16px;
}

.set-card {
  background: var(--card);
  border-radius: var(--radius);
  padding: 28px 32px;
  box-shadow: var(--card-shadow);
  cursor: pointer;
  transition: all 0.35s var(--ease);
  display: flex;
  flex-direction: column;
  gap: 16px;
  position: relative;
}

.set-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--card-shadow-hover);
}

.set-card-body {
  flex: 1;
  min-width: 0;
}

.set-card-name {
  font-size: 1.25rem;
  font-weight: 700;
  letter-spacing: -0.03em;
  color: var(--txt);
  line-height: 1.3;
  margin-bottom: 6px;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.set-card-meta {
  font-size: 0.8125rem;
  color: var(--txt3);
  display: flex;
  gap: 16px;
}

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

.set-card-actions .btn { flex-shrink: 0; }
.set-card-actions .spacer { flex: 1; }

/* ----- Empty State ----- */
.empty-state {
  text-align: center;
  padding: 100px 20px;
  color: var(--txt3);
}

.empty-state-icon {
  width: 64px;
  height: 64px;
  margin: 0 auto 20px;
  border-radius: 50%;
  background: var(--bg3);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
}

.empty-state h2 {
  font-size: 1.25rem;
  font-weight: 600;
  letter-spacing: -0.03em;
  color: var(--txt2);
  margin-bottom: 8px;
}

.empty-state p {
  font-size: 0.9375rem;
  line-height: 1.6;
}

/* ----- Modal ----- */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.35);
  backdrop-filter: blur(4px);
  -webkit-backdrop-filter: blur(4px);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 200;
  padding: 24px;
}

.modal {
  background: var(--card);
  border-radius: var(--radius);
  padding: 32px;
  max-width: 600px;
  width: 100%;
  max-height: 85vh;
  overflow-y: auto;
  box-shadow: 0 16px 64px rgba(0,0,0,0.2);
}

.modal h2 {
  font-size: 1.25rem;
  font-weight: 700;
  letter-spacing: -0.03em;
  margin-bottom: 20px;
  color: var(--txt);
}

.modal-actions {
  display: flex;
  gap: 8px;
  justify-content: flex-end;
  margin-top: 24px;
}

/* ----- Tabs ----- */
.tabs {
  display: flex;
  gap: 0;
  margin-bottom: 24px;
  background: var(--bg3);
  border-radius: 100px;
  padding: 3px;
}

.tab {
  flex: 1;
  padding: 8px 16px;
  border: none;
  border-radius: 100px;
  background: transparent;
  color: var(--txt2);
  font-family: var(--font);
  font-size: 0.8125rem;
  font-weight: 500;
  letter-spacing: -0.01em;
  cursor: pointer;
  transition: all 0.25s var(--ease);
  text-align: center;
}

.tab:hover { color: var(--txt); }
.tab.active {
  background: var(--card);
  color: var(--txt);
  box-shadow: 0 1px 3px rgba(0,0,0,0.08);
}

/* ----- Forms ----- */
.form-group { margin-bottom: 18px; }

.form-label {
  display: block;
  font-size: 0.8125rem;
  font-weight: 600;
  letter-spacing: -0.01em;
  color: var(--txt2);
  margin-bottom: 6px;
}

.form-input, .form-textarea {
  width: 100%;
  padding: 12px 16px;
  background: var(--bg);
  border: 1px solid var(--hairline);
  border-radius: var(--radius-xs);
  color: var(--txt);
  font-family: var(--font);
  font-size: 0.9375rem;
  letter-spacing: -0.01em;
  transition: all 0.2s var(--ease);
  -webkit-appearance: none;
}

.form-input:focus, .form-textarea:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-bg);
}

.form-textarea { resize: vertical; min-height: 140px; line-height: 1.6; }

/* ----- Card Browser ----- */
.browse-header {
  display: flex;
  align-items: flex-start;
  gap: 24px;
  margin-bottom: 40px;
  flex-wrap: wrap;
}

.browse-header .btn { flex-shrink: 0; margin-top: 4px; }

.browse-meta {
  flex: 1;
  min-width: 200px;
}

.browse-meta .page-title { margin-bottom: 4px; }

.browse-stats {
  font-size: 0.875rem;
  color: var(--txt3);
  letter-spacing: -0.01em;
}

.browse-stats span { color: var(--txt2); font-weight: 500; }

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

/* Flip Card */
.flip-container {
  perspective: 1200px;
  max-width: 620px;
  margin: 0 auto 32px;
}

.flip-card {
  position: relative;
  width: 100%;
  height: 340px;
  cursor: pointer;
  transition: transform 0.6s var(--ease);
  transform-style: preserve-3d;
}

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

.flip-face {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 48px;
  background: var(--card);
  border-radius: var(--radius);
  box-shadow: var(--card-shadow);
  backface-visibility: hidden;
  text-align: center;
}

.flip-back { transform: rotateY(180deg); }

.flip-label {
  font-size: 0.6875rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--txt3);
  margin-bottom: 16px;
}

.flip-text {
  font-size: 2.5rem;
  font-weight: 700;
  letter-spacing: -0.04em;
  line-height: 1.2;
  color: var(--txt);
  word-break: break-word;
}

/* Card nav */
.card-nav {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 16px;
  margin-bottom: 24px;
}

.card-counter {
  font-size: 0.875rem;
  color: var(--txt3);
  min-width: 80px;
  text-align: center;
  font-variant-numeric: tabular-nums;
}

/* View toggle */
.view-toggle-row {
  text-align: center;
  margin-bottom: 24px;
}

/* Card table */
.card-table-wrap {
  background: var(--card);
  border-radius: var(--radius);
  box-shadow: var(--card-shadow);
  overflow: hidden;
}

.card-list {
  width: 100%;
  border-collapse: collapse;
  table-layout: fixed;
}

.card-list th {
  text-align: left;
  padding: 14px 20px;
  font-size: 0.6875rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--txt3);
  background: var(--bg);
  border-bottom: 1px solid var(--hairline);
}

.card-list td {
  padding: 14px 20px;
  border-bottom: 1px solid var(--hairline);
  font-size: 0.875rem;
  letter-spacing: -0.01em;
  vertical-align: middle;
}

.card-list tr:last-child td { border-bottom: none; }
.card-list tbody tr:hover td { background: var(--bg); }

.card-list .term-col { width: 28%; font-weight: 600; color: var(--txt); }
.card-list .def-col { width: 46%; color: var(--txt2); }
.card-list .actions-col { width: 26%; text-align: right; white-space: nowrap; }

.card-list .actions-col .btn { display: inline-flex; }

/* Mastery dot */
.mastery-dot {
  display: inline-block;
  width: 6px; height: 6px;
  border-radius: 50%;
  margin-right: 6px;
  vertical-align: middle;
}
.mastery-dot.weak     { background: var(--danger); }
.mastery-dot.learning { background: var(--warning); }
.mastery-dot.mastered { background: var(--success); }
.mastery-dot.new      { background: var(--txt3); }

/* ----- Practice Mode ----- */
.practice-container { max-width: 620px; margin: 0 auto; }

.practice-progress { margin-bottom: 32px; }

.progress-bar {
  width: 100%;
  height: 4px;
  background: var(--bg3);
  border-radius: 2px;
  overflow: hidden;
  margin-bottom: 10px;
}

.progress-bar-fill {
  height: 100%;
  background: var(--accent);
  border-radius: 2px;
  transition: width 0.4s var(--ease);
}

.progress-text {
  font-size: 0.8125rem;
  color: var(--txt3);
  text-align: center;
  font-variant-numeric: tabular-nums;
}

/* Practice card */
.practice-card {
  background: var(--card);
  border-radius: var(--radius);
  box-shadow: var(--card-shadow);
  padding: 56px 48px;
  text-align: center;
  margin-bottom: 24px;
}

.practice-word {
  font-size: 3rem;
  font-weight: 700;
  letter-spacing: -0.04em;
  line-height: 1.1;
  color: var(--txt);
  margin-bottom: 10px;
}

.practice-hint {
  font-size: 0.875rem;
  color: var(--txt3);
  letter-spacing: -0.01em;
}

/* Answer area */
.answer-row {
  display: flex;
  gap: 8px;
  margin-bottom: 12px;
}

.answer-row .form-input { flex: 1; font-size: 1rem; padding: 14px 18px; }

.answer-actions {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

/* Feedback */
.feedback-card {
  border-radius: var(--radius-sm);
  padding: 24px;
  margin-top: 20px;
}

.feedback-card.correct {
  background: var(--success-bg);
  border: 1px solid rgba(48,209,88,0.2);
}
.feedback-card.incorrect {
  background: var(--danger-bg);
  border: 1px solid rgba(255,69,58,0.2);
}

.feedback-header {
  font-size: 1.125rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 8px;
}

.feedback-card.correct .feedback-header { color: var(--success); }
.feedback-card.incorrect .feedback-header { color: var(--danger); }

.feedback-ex {
  font-size: 0.9375rem;
  color: var(--txt2);
  line-height: 1.7;
  margin-bottom: 14px;
  letter-spacing: -0.01em;
}

.feedback-ref {
  font-size: 0.8125rem;
  color: var(--txt3);
  padding-top: 12px;
  border-top: 1px solid var(--hairline);
  letter-spacing: -0.01em;
}

.feedback-ref strong { color: var(--txt); font-weight: 600; }

/* ----- Session Summary ----- */
.summary {
  max-width: 560px;
  margin: 0 auto;
  text-align: center;
  padding: 60px 20px;
}

.summary-score {
  font-size: 5rem;
  font-weight: 700;
  letter-spacing: -0.05em;
  line-height: 1;
  margin-bottom: 10px;
}

.summary-label {
  font-size: 1.125rem;
  color: var(--txt2);
  letter-spacing: -0.02em;
  margin-bottom: 32px;
}

.summary-detail {
  display: inline-flex;
  gap: 40px;
  margin-bottom: 40px;
}

.summary-detail-item { text-align: center; }

.summary-detail-value {
  font-size: 1.75rem;
  font-weight: 700;
  letter-spacing: -0.03em;
  font-variant-numeric: tabular-nums;
}

.summary-detail-label {
  font-size: 0.8125rem;
  color: var(--txt3);
  margin-top: 2px;
}

.summary-actions {
  display: flex;
  gap: 12px;
  justify-content: center;
  flex-wrap: wrap;
  margin-bottom: 40px;
}

/* Answer review list */
.answer-review-list {
  text-align: left;
  max-width: 600px;
  margin: 0 auto;
}

.answer-review-list h3 {
  font-size: 1.1rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 16px;
  color: var(--txt);
}

.answer-review-item {
  padding: 16px 20px;
  margin-bottom: 8px;
  background: var(--card);
  border-radius: var(--radius-sm);
  box-shadow: var(--card-shadow);
}

.answer-review-item .word {
  font-weight: 600;
  color: var(--txt);
  margin-bottom: 4px;
}

.answer-review-item .user-answer {
  font-size: 0.875rem;
  color: var(--txt2);
}

.answer-review-item .reference {
  font-size: 0.8125rem;
  color: var(--txt3);
}

.answer-review-item .ai-note {
  font-size: 0.8125rem;
  color: var(--txt3);
  margin-top: 4px;
  font-style: italic;
}

/* ----- Stats Dashboard ----- */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 16px;
  margin-bottom: 40px;
}

.stat-card {
  background: var(--card);
  border-radius: var(--radius);
  box-shadow: var(--card-shadow);
  padding: 28px 32px;
  text-align: center;
}

.stat-value {
  font-size: 2.5rem;
  font-weight: 700;
  letter-spacing: -0.04em;
  line-height: 1;
  margin-bottom: 6px;
  font-variant-numeric: tabular-nums;
}

.stat-label {
  font-size: 0.8125rem;
  color: var(--txt3);
  letter-spacing: -0.01em;
}

.stat-value.accent  { color: var(--accent); }
.stat-value.success { color: var(--success); }
.stat-value.warning { color: var(--warning); }

.mastery-banner {
  background: var(--card);
  border-radius: var(--radius);
  box-shadow: var(--card-shadow);
  padding: 40px 48px;
  text-align: center;
}

.mastery-banner h3 {
  font-size: 1rem;
  font-weight: 600;
  letter-spacing: -0.02em;
  color: var(--txt2);
  margin-bottom: 16px;
}

.mastery-big-number {
  font-size: 3.5rem;
  font-weight: 700;
  letter-spacing: -0.05em;
  line-height: 1;
}

.mastery-banner .progress-bar {
  max-width: 400px;
  margin: 16px auto 0;
  height: 6px;
  border-radius: 3px;
}

/* ----- Sessions List ----- */
.session-list { display: flex; flex-direction: column; gap: 8px; }

.session-item {
  background: var(--card);
  border-radius: var(--radius-sm);
  box-shadow: var(--card-shadow);
  padding: 18px 24px;
  display: flex;
  align-items: center;
  gap: 20px;
  cursor: pointer;
  transition: all 0.25s var(--ease);
}

.session-item:hover {
  transform: translateY(-1px);
  box-shadow: var(--card-shadow-hover);
}

.session-set {
  font-weight: 600;
  letter-spacing: -0.02em;
  min-width: 160px;
  color: var(--txt);
}

.session-mode {
  font-size: 0.75rem;
  font-weight: 500;
  padding: 3px 10px;
  border-radius: 100px;
  background: var(--bg3);
  color: var(--txt2);
}

.session-date {
  font-size: 0.875rem;
  color: var(--txt3);
  margin-left: auto;
}

.session-score {
  font-weight: 700;
  font-size: 0.9375rem;
  min-width: 50px;
  text-align: right;
  font-variant-numeric: tabular-nums;
}

/* ----- Toast ----- */
#toast-container {
  position: fixed;
  bottom: 24px;
  right: 24px;
  z-index: 300;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.toast {
  background: var(--card);
  border-radius: var(--radius-sm);
  padding: 14px 24px;
  box-shadow: 0 8px 32px rgba(0,0,0,0.15);
  font-size: 0.875rem;
  letter-spacing: -0.01em;
  color: var(--txt);
  max-width: 380px;
  animation: toastIn 0.35s var(--ease);
}

.toast.success { border-left: 3px solid var(--success); }
.toast.error   { border-left: 3px solid var(--danger); }
.toast.info    { border-left: 3px solid var(--accent); }

@keyframes toastIn {
  from { opacity: 0; transform: translateX(32px); }
  to   { opacity: 1; transform: translateX(0); }
}

/* ----- Utility ----- */
.hidden    { display: none !important; }
.text-muted { color: var(--txt3); }
.text-center { text-align: center; }
.mt-8  { margin-top: 8px; }
.mt-12 { margin-top: 12px; }
.mt-16 { margin-top: 16px; }
.mt-24 { margin-top: 24px; }
.mt-32 { margin-top: 32px; }
.mb-8  { margin-bottom: 8px; }
.mb-16 { margin-bottom: 16px; }
.mb-24 { margin-bottom: 24px; }
.flex { display: flex; }
.gap-8  { gap: 8px; }
.gap-12 { gap: 12px; }
.gap-16 { gap: 16px; }
.flex-wrap { flex-wrap: wrap; }
.flex-1 { flex: 1; }
.items-center { align-items: center; }

/* ----- Inline Edit ----- */
.inline-edit {
  display: inline-flex;
  gap: 4px;
  align-items: center;
}

.inline-edit input {
  padding: 4px 8px;
  background: var(--bg);
  border: 1px solid var(--accent);
  border-radius: 4px;
  color: var(--txt);
  font-family: var(--font);
  font-size: 0.875rem;
}

/* Clickable cells for inline editing */
.click-edit {
  cursor: pointer;
  border-radius: 4px;
  padding: 2px 6px;
  margin: -2px -6px;
  transition: background 0.15s var(--ease);
  display: inline-block;
  max-width: 100%;
  word-break: break-word;
}
.click-edit:hover {
  background: var(--accent-bg);
}

/* Inline edit input inside table cells */
.inline-input {
  width: 100%;
  padding: 5px 8px;
  background: var(--bg);
  border: 1.5px solid var(--accent);
  border-radius: 5px;
  color: var(--txt);
  font-family: var(--font);
  font-size: 0.875rem;
  letter-spacing: -0.01em;
  outline: none;
  box-shadow: 0 0 0 3px var(--accent-bg);
}
.inline-input.def-input { font-size: 0.875rem; }

/* Editable title */
.editable-title {
  cursor: pointer;
  border-radius: 6px;
  padding: 2px 8px;
  margin: -2px -8px;
  transition: background 0.15s var(--ease);
}
.editable-title:hover {
  background: var(--accent-bg);
}

/* Add card row */
.card-row--add td {
  background: var(--bg) !important;
  padding: 10px 20px !important;
}
.card-row--add .form-input--table {
  width: 100%;
  padding: 8px 12px;
  font-size: 0.875rem;
  background: var(--card);
}
.card-row--add:hover td {
  background: var(--bg) !important;
}

/* ----- Responsive ----- */
@media (max-width: 768px) {
  .app-header {
    padding: 0 20px;
    flex-wrap: wrap;
    height: auto;
    padding-top: 12px;
    padding-bottom: 12px;
  }

  #main-content { padding: 24px 16px; }

  .flip-card { height: 260px; }
  .flip-text { font-size: 1.75rem; }
  .flip-face { padding: 28px; }

  .practice-word { font-size: 2rem; }
  .practice-card { padding: 36px 24px; }

  .set-grid { grid-template-columns: 1fr; }
  .set-card { padding: 20px 24px; }

  .card-list th, .card-list td { padding: 10px 12px; }
  .card-list { font-size: 0.8125rem; }

  .stats-grid { grid-template-columns: repeat(2, 1fr); }
  .stat-card { padding: 20px; }

  .session-item { flex-wrap: wrap; gap: 8px; }
  .session-set { min-width: auto; flex: 1; }

  .browse-header { flex-direction: column; gap: 12px; }
  .browse-actions { width: 100%; }
  .summary-score { font-size: 3.5rem; }
  .summary-detail { gap: 24px; }
}