/* ============================================================
   Lumina HSK — Design System
   ============================================================ */

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

:root {
  /* ---- Surfaces ---- */
  --bg:           #f0f2f7;
  --surface:      #ffffff;
  --surface-low:  #f6f7fb;
  --surface-mid:  #eef0f5;

  /* ---- Text ---- */
  --on-surface:         #1b1c1c;
  --on-surface-variant: #414751;
  --on-surface-muted:   #717783;

  /* ---- Primary (blue) ---- */
  --primary:    #005da7;
  --primary-d:  #004483;
  --primary-l:  #dceaff;
  --primary-bg: #eef4fc;

  /* ---- Semantic ---- */
  --error:    #ba1a1a;
  --error-l:  #ffdad6;
  --error-on: #93000a;
  --success:  #166534;
  --success-l:#dcfce7;

  /* ---- Radii ---- */
  --r-sm:   4px;
  --r:      8px;
  --r-md:   12px;
  --r-lg:   16px;
  --r-xl:   24px;
  --r-full: 9999px;

  /* ---- Elevation (multi-layer shadows, no borders) ---- */
  --shadow-xs:   0 1px 2px rgba(0,0,0,0.05);
  --shadow-sm:   0 1px 3px rgba(0,0,0,0.05), 0 4px 12px rgba(0,0,0,0.07);
  --shadow-md:   0 2px 6px rgba(0,0,0,0.05), 0 10px 28px rgba(0,0,0,0.09);
  --shadow-lg:   0 4px 8px rgba(0,0,0,0.05), 0 20px 48px rgba(0,0,0,0.11);
  --shadow-card: 0 2px 4px rgba(0,0,0,0.04), 0 12px 32px rgba(0,0,0,0.09), 0 32px 72px rgba(0,0,0,0.07);
  --shadow-blue: 0 4px 16px rgba(0, 93, 167, 0.30);
  /* Selection ring — modern "active" pattern */
  --ring:        0 0 0 2px var(--primary), 0 0 0 4px rgba(0, 93, 167, 0.14);
}

body {
  font-family: 'Inter', system-ui, sans-serif;
  background: var(--bg);
  color: var(--on-surface);
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: flex-start;
  padding: 40px 16px 80px;
  -webkit-font-smoothing: antialiased;
}

.app {
  width: 100%;
  max-width: 480px;
}

/* ---- Screens ---- */
.screen { display: none; }
.screen.active {
  display: block;
  animation: fadeUp 0.25s ease;
}
@keyframes fadeUp {
  from { opacity: 0; transform: translateY(12px); }
  to   { opacity: 1; transform: translateY(0); }
}

/* ============================
   APP HEADER
   ============================ */
.app-header {
  display: flex;
  align-items: center;
  gap: 14px;
  margin-bottom: 24px;
}
.logo-badge {
  font-family: 'Noto Sans SC', 'PingFang SC', sans-serif;
  font-size: 24px;
  font-weight: 700;
  color: var(--primary);
  background: var(--primary-l);
  width: 48px;
  height: 48px;
  border-radius: var(--r-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}
.app-title {
  font-size: 20px;
  font-weight: 600;
  letter-spacing: -0.02em;
}
.app-subtitle {
  font-size: 12px;
  font-weight: 500;
  color: var(--on-surface-muted);
  margin-top: 2px;
}

/* ============================
   SETUP CARD
   Floats above bg — shadow, no border
   ============================ */
.setup-card {
  background: var(--surface);
  border-radius: var(--r-md);
  box-shadow: var(--shadow-md);
}

.setup-section {
  padding: 22px 24px;
  border-bottom: 1px solid rgba(0,0,0,0.06);
}
.setup-section:last-child { border-bottom: none; }
/* Softer internal dividers than outline borders */

.section-label {
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--on-surface-muted);
  margin-bottom: 12px;
}

/* ---- HSK Level Cards ---- */
.level-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 8px;
  margin-bottom: 8px;
}
.btn-level {
  padding: 14px 8px;
  border-radius: var(--r);
  border: none;
  background: var(--surface-low);
  cursor: pointer;
  text-align: center;
  line-height: 1;
  transition: transform 0.14s ease, box-shadow 0.14s ease, background 0.14s ease;
  box-shadow: var(--shadow-xs);
}
.btn-level:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-sm);
  background: var(--surface);
}
.btn-level.active {
  background: var(--primary-bg);
  box-shadow: var(--ring);
  transform: translateY(-1px);
}

.level-name {
  display: block;
  font-size: 13px;
  font-weight: 600;
  color: var(--on-surface-variant);
  font-family: inherit;
}
.btn-level.active .level-name { color: var(--primary); }
.level-count {
  display: block;
  font-size: 10.5px;
  color: var(--on-surface-muted);
  margin-top: 4px;
  font-weight: 400;
}
.btn-level.active .level-count { color: var(--primary); opacity: 0.75; }

/* ---- Combo button (full-width pill) ---- */
.btn-combo {
  width: 100%;
  padding: 10px;
  border-radius: var(--r-full);
  border: none;
  background: var(--surface-low);
  color: var(--on-surface-muted);
  font-family: inherit;
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  box-shadow: var(--shadow-xs);
  transition: background 0.12s, box-shadow 0.12s, color 0.12s, transform 0.12s;
}
.btn-combo:hover { background: var(--surface); box-shadow: var(--shadow-sm); color: var(--on-surface-variant); }
.btn-combo.active {
  background: var(--primary);
  color: #fff;
  box-shadow: var(--shadow-blue);
}

/* ---- Combo panel ---- */
.combo-panel {
  max-height: 0;
  overflow: hidden;
  opacity: 0;
  transition: max-height 0.28s ease, opacity 0.22s ease;
}
.combo-panel.visible { max-height: 300px; opacity: 1; }

.combo-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 7px;
  margin-top: 10px;
  padding-bottom: 4px;
}
.combo-item {
  display: flex;
  align-items: center;
  gap: 9px;
  padding: 9px 11px;
  border-radius: var(--r);
  border: none;
  background: var(--surface-low);
  cursor: pointer;
  box-shadow: var(--shadow-xs);
  transition: box-shadow 0.12s, background 0.12s, transform 0.12s;
  user-select: none;
}
.combo-item:hover { background: var(--surface); box-shadow: var(--shadow-sm); }
.combo-item:has(.combo-check:checked) {
  background: var(--primary-bg);
  box-shadow: inset 0 0 0 2px var(--primary);
}
.combo-item .combo-check { display: none; }

.check-box {
  width: 16px;
  height: 16px;
  border-radius: var(--r-sm);
  border: 1.5px solid rgba(0,0,0,0.15);
  flex-shrink: 0;
  background: var(--surface);
  transition: all 0.12s;
  position: relative;
}
.combo-item:has(.combo-check:checked) .check-box {
  background: var(--primary);
  border-color: var(--primary);
}
.combo-item:has(.combo-check:checked) .check-box::after {
  content: '';
  position: absolute;
  width: 8px;
  height: 5px;
  border-left: 1.5px solid #fff;
  border-bottom: 1.5px solid #fff;
  top: 3px;
  left: 3px;
  transform: rotate(-45deg);
}
.combo-label {
  font-size: 12.5px;
  font-weight: 600;
  color: var(--on-surface-variant);
  line-height: 1;
}
.combo-item:has(.combo-check:checked) .combo-label { color: var(--primary); }
.combo-label small {
  display: block;
  font-size: 10.5px;
  font-weight: 400;
  color: var(--on-surface-muted);
  margin-top: 2px;
}

/* ---- Selection chips (pill, no border) ---- */
.btn-group {
  display: flex;
  gap: 7px;
  flex-wrap: wrap;
}
.btn-opt {
  flex: 1;
  min-width: 56px;
  padding: 9px 12px;
  border-radius: var(--r-full);
  border: none;
  background: var(--surface-low);
  color: var(--on-surface-muted);
  font-family: inherit;
  font-size: 13px;
  font-weight: 500;
  cursor: pointer;
  box-shadow: var(--shadow-xs);
  transition: background 0.12s, box-shadow 0.12s, color 0.12s;
  text-align: center;
  white-space: nowrap;
  line-height: 1;
}
.btn-opt:hover { background: var(--surface); box-shadow: var(--shadow-sm); color: var(--on-surface-variant); }
.btn-opt.active {
  background: var(--primary);
  color: #fff;
  box-shadow: var(--shadow-blue);
}

/* ---- Shuffle toggle ---- */
.shuffle-row {
  max-height: 0;
  overflow: hidden;
  opacity: 0;
  transition: max-height 0.22s ease, opacity 0.18s ease;
}
.shuffle-row.visible { max-height: 60px; opacity: 1; }

.shuffle-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-top: 10px;
  padding: 11px 13px;
  background: var(--surface-low);
  border-radius: var(--r);
}
.shuffle-label-text {
  font-size: 13px;
  font-weight: 500;
  color: var(--on-surface-variant);
}
.toggle-switch {
  position: relative;
  width: 38px;
  height: 21px;
  flex-shrink: 0;
}
.toggle-switch input {
  position: absolute;
  inset: 0;
  opacity: 0;
  cursor: pointer;
  z-index: 1;
  margin: 0;
  width: 100%;
  height: 100%;
}
.toggle-track {
  display: block;
  width: 100%;
  height: 100%;
  border-radius: var(--r-full);
  background: rgba(0,0,0,0.15);
  transition: background 0.18s;
  position: relative;
}
.toggle-track::after {
  content: '';
  position: absolute;
  width: 15px;
  height: 15px;
  background: #fff;
  border-radius: 50%;
  top: 3px;
  left: 3px;
  transition: transform 0.18s;
  box-shadow: 0 1px 4px rgba(0,0,0,0.25);
}
.toggle-switch input:checked ~ .toggle-track { background: var(--primary); }
.toggle-switch input:checked ~ .toggle-track::after { transform: translateX(17px); }

/* ---- Custom count ---- */
.count-custom {
  margin-top: 14px;
  padding-top: 14px;
  border-top: 1px solid rgba(0,0,0,0.06);
}
.count-label {
  display: block;
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--on-surface-muted);
  margin-bottom: 6px;
}
.count-input {
  width: 100%;
  height: 44px;
  padding: 0 12px;
  border-radius: var(--r);
  border: none;
  background: var(--surface-low);
  box-shadow: inset 0 0 0 1px rgba(0,0,0,0.08);
  font-family: inherit;
  font-size: 14px;
  color: var(--on-surface);
  outline: none;
  transition: box-shadow 0.15s;
  -moz-appearance: textfield;
}
.count-input::-webkit-inner-spin-button,
.count-input::-webkit-outer-spin-button { -webkit-appearance: none; }
.count-input:focus {
  box-shadow: inset 0 0 0 1.5px var(--primary), 0 0 0 3px rgba(0, 93, 167, 0.12);
}
.count-hint {
  font-size: 11.5px;
  color: var(--on-surface-muted);
  margin-top: 5px;
}

/* Count section dimmed when range overrides it */
#count-section.count-overridden .btn-group,
#count-section.count-overridden .count-custom {
  opacity: 0.35;
  pointer-events: none;
  user-select: none;
}

/* ---- Word range row (appears when ordered) ---- */
.range-row {
  max-height: 0;
  overflow: hidden;
  opacity: 0;
  transition: max-height 0.26s ease, opacity 0.2s ease;
}
.range-row.visible {
  max-height: 140px;
  opacity: 1;
}
.range-inner {
  padding-top: 14px;
  border-top: 1px solid rgba(0,0,0,0.06);
  margin-top: 14px;
}
.range-inputs {
  display: flex;
  align-items: flex-end;
  gap: 10px;
}
.range-field { flex: 1; }
.range-field-label {
  display: block;
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--on-surface-muted);
  margin-bottom: 6px;
}
.range-input {
  width: 100%;
  height: 44px;
  padding: 0 12px;
  border-radius: var(--r);
  border: none;
  background: var(--surface-low);
  box-shadow: inset 0 0 0 1px rgba(0,0,0,0.08);
  font-family: inherit;
  font-size: 14px;
  color: var(--on-surface);
  outline: none;
  transition: box-shadow 0.15s;
  -moz-appearance: textfield;
}
.range-input::-webkit-inner-spin-button,
.range-input::-webkit-outer-spin-button { -webkit-appearance: none; }
.range-input:focus {
  box-shadow: inset 0 0 0 1.5px var(--primary), 0 0 0 3px rgba(0, 93, 167, 0.12);
}
.range-arrow {
  font-size: 14px;
  color: var(--on-surface-muted);
  padding-bottom: 12px;
  flex-shrink: 0;
}

/* ---- Start button ---- */
.btn-start {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  width: 100%;
  padding: 14px;
  border-radius: var(--r);
  border: none;
  background: var(--primary);
  color: #fff;
  font-family: inherit;
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  letter-spacing: 0.01em;
  box-shadow: var(--shadow-blue);
  transition: background 0.14s, transform 0.14s, box-shadow 0.14s;
}
.btn-start:hover {
  background: var(--primary-d);
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(0, 93, 167, 0.38);
}
.btn-start:active { transform: translateY(0); box-shadow: var(--shadow-blue); }

/* ============================
   LOADING
   ============================ */
#loading-screen {
  text-align: center;
  padding: 80px 0;
  color: var(--on-surface-muted);
}
.spinner {
  width: 32px;
  height: 32px;
  border: 2.5px solid rgba(0,0,0,0.08);
  border-top-color: var(--primary);
  border-radius: 50%;
  animation: spin 0.7s linear infinite;
  margin: 0 auto 16px;
}
@keyframes spin { to { transform: rotate(360deg); } }
.loading-text { font-size: 14px; font-weight: 500; }

/* ============================
   FLASHCARD SCREEN
   ============================ */
.fc-topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 16px;
}
.btn-back {
  display: flex;
  align-items: center;
  gap: 4px;
  background: var(--surface);
  border: none;
  border-radius: var(--r-full);
  padding: 7px 14px;
  font-family: inherit;
  font-size: 12.5px;
  font-weight: 500;
  color: var(--on-surface-muted);
  cursor: pointer;
  box-shadow: var(--shadow-sm);
  transition: box-shadow 0.12s, color 0.12s, transform 0.12s;
}
.btn-back:hover { box-shadow: var(--shadow-md); color: var(--on-surface-variant); transform: translateY(-1px); }

.fc-counter {
  font-size: 13px;
  font-weight: 500;
  color: var(--on-surface-muted);
}
.fc-counter strong { color: var(--on-surface); font-weight: 700; font-size: 14px; }

.progress-track {
  height: 3px;
  background: rgba(0,0,0,0.08);
  border-radius: var(--r-full);
  margin-bottom: 20px;
  overflow: hidden;
}
.progress-fill {
  height: 100%;
  background: var(--primary);
  border-radius: var(--r-full);
  transition: width 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}

/* ---- Flashcard — the hero, deep shadow ---- */
.card-scene {
  perspective: 1400px;
  margin-bottom: 13px;
  cursor: pointer;
}
.flashcard {
  position: relative;
  width: 100%;
  height: 320px;
  transform-style: preserve-3d;
  transition: transform 0.52s cubic-bezier(0.4, 0, 0.2, 1);
  outline: none;
}
.flashcard.flipped { transform: rotateY(180deg); }

.card-face {
  position: absolute;
  inset: 0;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  border-radius: var(--r-xl);
  background: var(--surface);
  box-shadow: var(--shadow-card);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 32px 24px;
  user-select: none;
  transition: box-shadow 0.2s ease;
}
.card-scene:hover .card-face {
  box-shadow: 0 4px 8px rgba(0,0,0,0.06), 0 20px 48px rgba(0,0,0,0.13), 0 40px 80px rgba(0,0,0,0.08);
}
.card-back-face { transform: rotateY(180deg); }

/* Status badge */
.card-status {
  position: absolute;
  top: 14px;
  right: 14px;
  font-size: 10.5px;
  font-weight: 600;
  padding: 3px 9px;
  border-radius: var(--r-full);
  display: none;
  letter-spacing: 0.02em;
}
.card-status.known-badge   { background: var(--success-l); color: var(--success); display: inline; }
.card-status.unknown-badge { background: var(--error-l);   color: var(--error-on); display: inline; }

/* Level badge (combo mode) */
.word-level-badge {
  position: absolute;
  top: 14px;
  left: 14px;
  font-size: 10px;
  font-weight: 700;
  padding: 3px 9px;
  border-radius: var(--r-full);
  background: var(--primary-l);
  color: var(--primary-d);
  display: none;
  letter-spacing: 0.03em;
}
.word-level-badge.visible { display: inline; }

.hanzi {
  font-family: 'Noto Sans SC', 'PingFang SC', 'Microsoft YaHei', sans-serif;
  font-size: 96px;
  font-weight: 700;
  line-height: 1;
  color: var(--on-surface);
}
.front-hint {
  margin-top: 24px;
  font-size: 12px;
  font-weight: 500;
  color: var(--on-surface-muted);
  display: flex;
  align-items: center;
  gap: 6px;
  letter-spacing: 0.02em;
}
.hint-dot {
  width: 5px;
  height: 5px;
  border-radius: 50%;
  background: rgba(0,0,0,0.15);
  animation: pulse 2s ease-in-out infinite;
}
@keyframes pulse {
  0%, 100% { opacity: 0.3; transform: scale(1); }
  50%       { opacity: 1;   transform: scale(1.5); }
}

.pinyin {
  font-size: 26px;
  font-weight: 500;
  color: var(--primary);
  margin: 14px 0 4px;
  letter-spacing: 1px;
}
.translation {
  font-size: 16px;
  font-weight: 400;
  color: var(--on-surface-variant);
  text-align: center;
  line-height: 1.65;
  max-width: 270px;
}

/* ---- Assess + Nav rows ---- */
.assess-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
  margin-bottom: 8px;
  opacity: 0;
  transform: translateY(8px);
  transition: opacity 0.22s ease, transform 0.22s ease;
  pointer-events: none;
}
.assess-row.visible { opacity: 1; transform: translateY(0); pointer-events: auto; }

.btn-assess {
  padding: 12px;
  border-radius: var(--r);
  border: none;
  font-family: inherit;
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  transition: transform 0.12s, box-shadow 0.12s;
}
.btn-review {
  color: var(--error);
  background: var(--error-l);
  box-shadow: 0 1px 3px rgba(186, 26, 26, 0.12), 0 4px 10px rgba(186, 26, 26, 0.08);
}
.btn-review:hover {
  transform: translateY(-1px);
  box-shadow: 0 2px 6px rgba(186, 26, 26, 0.18), 0 8px 16px rgba(186, 26, 26, 0.10);
}
.btn-know {
  color: var(--success);
  background: var(--success-l);
  box-shadow: 0 1px 3px rgba(22, 101, 52, 0.12), 0 4px 10px rgba(22, 101, 52, 0.08);
}
.btn-know:hover {
  transform: translateY(-1px);
  box-shadow: 0 2px 6px rgba(22, 101, 52, 0.18), 0 8px 16px rgba(22, 101, 52, 0.10);
}

.nav-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
  margin-bottom: 12px;
}
.btn-nav {
  padding: 11px;
  border-radius: var(--r);
  border: none;
  background: var(--surface);
  box-shadow: var(--shadow-sm);
  font-family: inherit;
  font-size: 13px;
  font-weight: 500;
  color: var(--on-surface-variant);
  cursor: pointer;
  transition: box-shadow 0.12s, transform 0.12s;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 4px;
}
.btn-nav:hover:not(:disabled) { box-shadow: var(--shadow-md); transform: translateY(-1px); }
.btn-nav:disabled { opacity: 0.3; cursor: not-allowed; box-shadow: none; }

.kbd-hint {
  text-align: center;
  font-size: 11px;
  font-weight: 500;
  color: var(--on-surface-muted);
}
.touch-hint {
  display: none;
}

/* Touch devices: swap hints */
@media (hover: none) and (pointer: coarse) {
  .kbd-hint { display: none; }
  .touch-hint {
    display: flex;
    justify-content: space-between;
    font-size: 11px;
    font-weight: 500;
    color: var(--on-surface-muted);
    padding: 0 4px;
  }
}
kbd {
  display: inline-block;
  padding: 2px 5px;
  border-radius: var(--r-sm);
  font-size: 10px;
  font-family: inherit;
  background: var(--surface);
  color: var(--on-surface-muted);
  box-shadow: var(--shadow-xs), inset 0 -1px 0 rgba(0,0,0,0.1);
}

/* ============================
   RESULTS
   ============================ */
.results-card {
  background: var(--surface);
  border-radius: var(--r-md);
  box-shadow: var(--shadow-md);
  padding: 32px 24px;
  text-align: center;
}
.results-emoji { font-size: 48px; margin-bottom: 12px; }
.results-title {
  font-size: 20px;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 6px;
}
.results-sub { font-size: 13px; font-weight: 500; color: var(--on-surface-muted); margin-bottom: 28px; }

.stats-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 8px;
  margin-bottom: 20px;
}
.stat-box {
  padding: 14px 8px;
  border-radius: var(--r);
  background: var(--surface-low);
  box-shadow: var(--shadow-xs);
}
.stat-num {
  font-size: 28px;
  font-weight: 800;
  line-height: 1;
  letter-spacing: -0.04em;
  color: var(--on-surface);
}
.stat-lbl {
  font-size: 11px;
  font-weight: 500;
  color: var(--on-surface-muted);
  margin-top: 4px;
}
.stat-box.s-known  .stat-num { color: var(--success); }
.stat-box.s-review .stat-num { color: var(--error); }

.score-bar {
  height: 4px;
  background: rgba(0,0,0,0.08);
  border-radius: var(--r-full);
  overflow: hidden;
  margin-bottom: 26px;
}
.score-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary-l), var(--primary));
  border-radius: var(--r-full);
  transition: width 0.9s cubic-bezier(0.4, 0, 0.2, 1);
}

.results-actions { display: flex; flex-direction: column; gap: 8px; }

.btn-primary {
  width: 100%;
  padding: 12px;
  border-radius: var(--r);
  border: none;
  background: var(--primary);
  color: #fff;
  font-family: inherit;
  font-size: 13.5px;
  font-weight: 600;
  cursor: pointer;
  box-shadow: var(--shadow-blue);
  transition: background 0.12s, transform 0.12s, box-shadow 0.12s;
}
.btn-primary:hover { background: var(--primary-d); transform: translateY(-1px); box-shadow: 0 6px 20px rgba(0,93,167,0.36); }

.btn-secondary {
  width: 100%;
  padding: 11px;
  border-radius: var(--r);
  border: none;
  background: var(--surface-low);
  color: var(--on-surface-variant);
  font-family: inherit;
  font-size: 13.5px;
  font-weight: 500;
  cursor: pointer;
  box-shadow: var(--shadow-xs);
  transition: box-shadow 0.12s, transform 0.12s;
}
.btn-secondary:hover { box-shadow: var(--shadow-sm); transform: translateY(-1px); }

/* ============================
   RESPONSIVE
   ============================ */
@media (max-width: 400px) {
  .hanzi { font-size: 78px; }
  .flashcard { height: 280px; }
  .setup-section { padding: 18px 18px; }
  body { padding: 20px 12px 56px; }
}
@media (max-width: 340px) {
  .btn-opt   { font-size: 11.5px; padding: 7px 8px; }
  .btn-level { padding: 10px 6px; }
  .level-name { font-size: 12px; }
}