/* ===== Design tokens =====
   Palette follows Apple's brand colors: Black/White, Space Gray (#555555),
   Silver Gray (#A6A6A6), blue accents (#0071e3 / #0066cc / #006edb), Athens
   Gray (#F5F5F7) as the light surface and Shark (#1D1D1F) as the dark surface.
   Silver Gray is below 4.5:1 on white, so it is only used for non-text UI
   (switch track, disabled states); text uses Space Gray / Shark. */
:root {
  color-scheme: light dark;

  --font-text: -apple-system, BlinkMacSystemFont, "SF Pro Text", "Helvetica Neue", Helvetica,
    Arial, sans-serif;
  --font-display: -apple-system, BlinkMacSystemFont, "SF Pro Display", "Helvetica Neue", Helvetica,
    Arial, sans-serif;

  --bg: #f5f5f7;
  --surface: #ffffff;
  --text: #1d1d1f;
  --text-2: #555555;
  --border: rgba(0, 0, 0, 0.12);
  --fill: rgba(0, 0, 0, 0.06);
  --fill-hover: rgba(0, 0, 0, 0.1);
  --silver: #a6a6a6;

  --accent: #0071e3;
  --accent-hover: #0066cc;
  --accent-depth: #006edb;
  --on-accent: #ffffff;
  --accent-text: #0066cc; /* blue used as text: needs >4.5:1 on the surface */
  --accent-soft: rgba(0, 113, 227, 0.12);

  --danger: #b3261e;
  --danger-soft: rgba(179, 38, 30, 0.1);

  --shadow-pop: 0 8px 30px rgba(0, 0, 0, 0.16);
  --header-bg: #f5f5f7;

  --radius-lg: 18px;
  --radius-md: 12px;
  --radius-sm: 9px;
  --ease: 180ms ease;
  --column: 780px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #000000;
    --surface: #1d1d1f;
    --text: #f5f5f7;
    --text-2: #a6a6a6;
    --border: rgba(255, 255, 255, 0.16);
    --fill: rgba(255, 255, 255, 0.1);
    --fill-hover: rgba(255, 255, 255, 0.16);
    --silver: #555555;

    --accent-text: #2997ff;
    --accent-soft: rgba(41, 151, 255, 0.18);

    --danger: #ff6961;
    --danger-soft: rgba(255, 105, 97, 0.16);

    --shadow-pop: 0 8px 30px rgba(0, 0, 0, 0.6);
    --header-bg: #000000;
  }
}

/* ===== Reset & base ===== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { -webkit-text-size-adjust: 100%; }
body {
  font-family: var(--font-text);
  font-size: 1rem;
  line-height: 1.4;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
}
button, input, textarea { font-family: inherit; color: inherit; }
button { -webkit-tap-highlight-color: transparent; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

/* ===== Layout helpers ===== */
.hidden { display: none !important; }
.centered {
  display: flex; flex-direction: column; align-items: center;
  justify-content: center; gap: 1rem; min-height: 60vh;
  text-align: center; padding: 2rem;
}
.view { display: flex; flex-direction: column; min-height: 100vh; width: 100%; min-width: 0; }

/* ===== Header (AppHeader) ===== */
.app-header {
  display: flex; align-items: center; gap: 0.5rem;
  height: calc(56px + env(safe-area-inset-top));
  padding: env(safe-area-inset-top) max(1rem, env(safe-area-inset-right)) 0
    max(1rem, env(safe-area-inset-left));
  background: var(--header-bg);
  position: sticky; top: 0; z-index: 10;
}
.app-header h1,
.app-header h2 {
  font-family: var(--font-display);
  font-size: 1.0625rem; font-weight: 600; flex: 1; letter-spacing: -0.01em;
  white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
}
.app-header > .btn-icon:first-child { margin-left: -0.5rem; }
.app-header .btn-icon:last-child { margin-right: -0.5rem; }
#study-progress { font-size: 0.875rem; color: var(--text-2); font-variant-numeric: tabular-nums; }

/* ===== Buttons ===== */
.btn {
  padding: 0.75rem 1.5rem; border: none; border-radius: 999px;
  font-size: 1rem; font-weight: 500; cursor: pointer; min-height: 44px;
  transition: background var(--ease), transform var(--ease), opacity var(--ease);
}
.btn:active { transform: scale(0.98); }
.btn:disabled { opacity: 0.5; cursor: default; }
.btn-primary { background: var(--accent); color: var(--on-accent); }
.btn-primary:hover { background: var(--accent-hover); }
.btn-primary:active { background: var(--accent-depth); }
.btn-secondary { background: var(--fill); color: var(--text); }
.btn-secondary:hover { background: var(--fill-hover); }
.btn-icon {
  background: none; border: none; color: var(--text); font-size: 1.25rem;
  cursor: pointer; border-radius: 50%;
  min-width: 44px; min-height: 44px;
  display: flex; align-items: center; justify-content: center;
  transition: background var(--ease), transform var(--ease);
}
.btn-icon:hover { background: var(--fill); }
.btn-icon:active { transform: scale(0.94); }

/* Header menu popover */
.menu-wrap { position: relative; }
.menu {
  position: absolute; right: 0; top: calc(100% + 4px); min-width: 160px;
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius-md); box-shadow: var(--shadow-pop); padding: 0.25rem;
}
.menu-item {
  display: block; width: 100%; text-align: left; background: none; border: none;
  padding: 0.65rem 0.75rem; border-radius: var(--radius-sm);
  font-size: 0.95rem; cursor: pointer; min-height: 44px;
}
.menu-item:hover { background: var(--fill); }

/* ===== Home ===== */
.home-main {
  flex: 1; display: flex; flex-direction: column; gap: 1.5rem;
  padding: 1.5rem 1rem calc(2rem + env(safe-area-inset-bottom));
  min-width: 0;
}
.greeting h2 {
  font-family: var(--font-display);
  font-size: 1.75rem; font-weight: 700; letter-spacing: -0.02em; line-height: 1.15;
}
.greeting p { color: var(--text-2); margin-top: 0.25rem; }

/* Hero / primary study card */
.hero {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius-lg); padding: 1.5rem;
  display: flex; flex-direction: column; align-items: flex-start;
}
.hero-eyebrow {
  font-size: 0.75rem; font-weight: 600; letter-spacing: 0.08em;
  text-transform: uppercase; color: var(--text-2);
}
.hero-count {
  font-family: var(--font-display);
  font-size: 2.5rem; font-weight: 700; letter-spacing: -0.03em; line-height: 1.1;
  margin-top: 0.5rem; font-variant-numeric: tabular-nums;
}
.hero-count span { font-size: 1.5rem; font-weight: 600; letter-spacing: -0.02em; }
.hero-sub { color: var(--text-2); margin-top: 0.125rem; }
.btn-cta { margin-top: 1.25rem; width: 100%; padding: 0.9rem 1.5rem; font-size: 1.0625rem; }
.arrow { display: inline-block; transition: transform var(--ease); }
.btn-cta:hover .arrow, .link-btn:hover .arrow { transform: translateX(3px); }

/* Compact metrics */
.metrics { display: grid; grid-template-columns: repeat(3, 1fr); gap: 0.5rem; }
.metric {
  display: flex; flex-direction: column-reverse; justify-content: flex-end;
  padding: 0 0.25rem;
}
.metric-number {
  font-family: var(--font-display);
  font-size: 1.5rem; font-weight: 600; letter-spacing: -0.02em; line-height: 1.2;
  font-variant-numeric: tabular-nums;
}
.metric-label { font-size: 0.8125rem; color: var(--text-2); }

/* Settings group */
.settings {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius-lg); overflow: hidden;
}
.settings-title {
  font-size: 0.75rem; font-weight: 600; letter-spacing: 0.08em; text-transform: uppercase;
  color: var(--text-2); padding: 1rem 1rem 0.25rem;
}
.setting-row {
  display: flex; flex-direction: column; gap: 0.5rem; padding: 0.875rem 1rem;
  border-top: 1px solid var(--border);
}
.settings-title + .setting-row { border-top: none; }
.setting-row-inline { flex-direction: row; align-items: center; justify-content: space-between; gap: 1rem; }
.setting-label { font-size: 0.9375rem; font-weight: 500; }
.setting-text { display: flex; flex-direction: column; gap: 0.125rem; min-width: 0; }
.setting-desc { font-size: 0.8125rem; color: var(--text-2); }

/* Section picker trigger */
.select-btn {
  display: flex; align-items: center; justify-content: space-between; gap: 0.5rem;
  width: 100%; min-height: 44px; padding: 0 0.875rem;
  background: var(--fill); border: none; border-radius: var(--radius-md);
  font-size: 0.9375rem; text-align: left; cursor: pointer;
  transition: background var(--ease), transform var(--ease);
}
.select-btn:hover { background: var(--fill-hover); }
.select-btn:active { transform: scale(0.99); }
.select-text { flex: 1; min-width: 0; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.select-caret { color: var(--text-2); font-size: 0.8rem; }

/* Segmented control (Normal / Reverse) */
.segmented {
  display: flex; background: var(--fill); border-radius: var(--radius-md); padding: 2px; gap: 2px;
}
.seg-btn {
  flex: 1; min-height: 40px; border: none; border-radius: 10px;
  background: transparent; color: var(--text-2);
  font-size: 0.9375rem; font-weight: 500; cursor: pointer;
  transition: background var(--ease), color var(--ease), box-shadow var(--ease);
}
.seg-btn:not(.active):hover { color: var(--text); }
.seg-btn.active {
  background: var(--surface); color: var(--text); font-weight: 600;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.2);
}
/* Checkmark so the active option is never signalled by color alone */
.seg-btn.active::before { content: "✓ "; }

/* Toggle switch */
.switch {
  position: relative; flex-shrink: 0; width: 51px; height: 31px;
  border: none; border-radius: 999px; background: var(--silver); cursor: pointer;
  transition: background var(--ease);
}
.switch[aria-checked="true"] { background: var(--accent); }
.switch-knob {
  position: absolute; top: 2px; left: 2px; width: 27px; height: 27px;
  border-radius: 50%; background: #fff; box-shadow: 0 1px 3px rgba(0, 0, 0, 0.3);
  transition: transform var(--ease);
}
.switch[aria-checked="true"] .switch-knob { transform: translateX(20px); }
/* 44px hit area without enlarging the visual switch */
.switch::after { content: ""; position: absolute; inset: -7px -4px; }

/* Review period filter row */
.filter-row {
  display: flex; gap: 0.25rem; overflow-x: auto; scrollbar-width: none;
  margin: 0 -1rem; padding: 0 1rem;
}
.filter-row::-webkit-scrollbar { display: none; }
.time-btn {
  flex-shrink: 0; min-height: 44px; padding: 0 0.875rem;
  border: none; border-radius: 999px; background: transparent; color: var(--text-2);
  font-size: 0.9375rem; font-weight: 500; cursor: pointer;
  transition: background var(--ease), color var(--ease);
}
.time-btn:not(.active):hover { background: var(--fill); color: var(--text); }
.time-btn.active { background: var(--accent-soft); color: var(--accent-text); font-weight: 600; }
.custom-date-input {
  width: 100%; min-height: 44px; padding: 0 0.875rem;
  border: 1px solid var(--border); border-radius: var(--radius-md);
  font-size: 0.9375rem; background: var(--surface); cursor: pointer;
}

/* Secondary link-style action */
.link-btn {
  align-self: center; background: none; border: none; cursor: pointer;
  color: var(--accent-text); font-size: 1rem; font-weight: 500;
  min-height: 44px; padding: 0 0.75rem; border-radius: 999px;
  transition: opacity var(--ease), transform var(--ease);
}
.link-btn:hover { text-decoration: underline; }
.link-btn:active { transform: scale(0.98); }

/* ===== Flashcard ===== */
.study-main { flex: 1; padding: 1.5rem 1rem; display: flex; flex-direction: column; gap: 1.5rem; }
.flashcard-scene {
  width: 100%; max-width: 440px; margin: 0 auto;
  /* clamp so the card never overflows on landscape phones */
  height: clamp(220px, 42vh, 340px); perspective: 1000px; cursor: pointer;
  border-radius: var(--radius-lg);
}
.flashcard-card {
  width: 100%; height: 100%;
  position: relative; transform-style: preserve-3d;
  transition: transform 0.45s cubic-bezier(0.32, 0.72, 0, 1);
  border-radius: var(--radius-lg);
}
.flashcard-scene.flipped .flashcard-card { transform: rotateY(180deg); }
.flashcard-front,
.flashcard-back {
  position: absolute; inset: 0;
  backface-visibility: hidden; -webkit-backface-visibility: hidden;
  border-radius: var(--radius-lg);
  display: flex; flex-direction: column; align-items: center; justify-content: center;
  padding: 1.5rem; text-align: center; overflow-y: auto;
  background: var(--surface); border: 1px solid var(--border);
}
.flashcard-back { transform: rotateY(180deg); }
.card-lang { font-size: 0.75rem; text-transform: uppercase; letter-spacing: 0.08em; color: var(--text-2); margin-bottom: 0.5rem; }
.card-word {
  font-family: var(--font-display);
  font-size: 2.25rem; font-weight: 700; letter-spacing: -0.02em;
  word-break: break-word; overflow-wrap: anywhere;
}
.card-hint { margin-top: 1rem; font-size: 0.8125rem; color: var(--text-2); }
.card-definition { font-size: 1.125rem; font-weight: 500; margin-bottom: 1rem; }
.card-example { font-size: 0.9375rem; color: var(--text-2); font-style: italic; }

/* ===== Rating buttons ===== */
.rating-buttons { max-width: 440px; margin: 0 auto; width: 100%; }
.rating-label { text-align: center; font-size: 0.875rem; color: var(--text-2); margin-bottom: 0.75rem; }
.rating-row { display: flex; gap: 0.375rem; justify-content: center; flex-wrap: wrap; }
.btn-rating {
  flex: 1 1 4.5rem; min-width: 0; padding: 0.6rem 0.25rem; min-height: 44px;
  border: none; border-radius: var(--radius-md); background: var(--fill); color: var(--text);
  font-size: 0.875rem; font-weight: 500; cursor: pointer;
  transition: background var(--ease), transform var(--ease);
}
.btn-rating:hover { background: var(--fill-hover); }
.btn-rating:active { transform: scale(0.96); }

.btn-edit-card {
  display: block; margin: 0.75rem auto 0; background: none; border: none;
  min-height: 44px; padding: 0 1rem; border-radius: 999px;
  font-size: 0.9375rem; font-weight: 500; color: var(--accent-text); cursor: pointer;
}
.btn-edit-card:hover { background: var(--accent-soft); }

/* ===== Browse ===== */
.browse-main { flex: 1; padding: 1rem; overflow-y: auto; }
.lang-group { margin-bottom: 1.5rem; }
.lang-heading {
  font-size: 0.75rem; font-weight: 600; text-transform: uppercase; letter-spacing: 0.08em;
  color: var(--text-2); padding: 0.5rem 0.25rem;
}
.lang-group > .word-item:first-of-type { border-top-left-radius: var(--radius-md); border-top-right-radius: var(--radius-md); }
.word-item { background: var(--surface); border-bottom: 1px solid var(--border); }
.lang-group > .word-item:first-of-type { border-top: 1px solid var(--border); }
.lang-group > .word-item:last-of-type {
  border-bottom-left-radius: var(--radius-md); border-bottom-right-radius: var(--radius-md);
}
.word-summary { display: flex; align-items: center; gap: 0.75rem; padding: 0.875rem 1rem; cursor: pointer; min-height: 44px; }
.word-text { flex: 1; min-width: 0; }
.word-title { font-size: 1.0625rem; font-weight: 600; }
.word-def {
  font-size: 0.875rem; color: var(--text-2); margin-top: 0.125rem;
  white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
}
.word-due { font-size: 0.75rem; color: var(--text-2); white-space: nowrap; }
.word-expand-icon { font-size: 0.9rem; color: var(--text-2); transition: transform var(--ease); }
.word-item.expanded .word-expand-icon { transform: rotate(180deg); }
.word-detail { padding: 0 1rem 1rem; display: none; }
.word-item.expanded .word-detail { display: block; }
.word-example { font-size: 0.9375rem; color: var(--text-2); font-style: italic; margin: 0 0 0.75rem; }
.btn-delete {
  font-size: 0.875rem; padding: 0.5rem 1rem; min-height: 44px;
  background: var(--danger-soft); color: var(--danger);
  border: none; border-radius: 999px; cursor: pointer; font-weight: 600;
  transition: opacity var(--ease), transform var(--ease);
}
.btn-delete:hover { opacity: 0.8; }
.btn-delete:active { transform: scale(0.98); }

/* ===== Login overlay ===== */
.login-overlay {
  position: fixed; inset: 0; z-index: 200;
  background: var(--bg);
  display: flex; align-items: center; justify-content: center;
  padding: 1.5rem;
}
.login-card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-lg);
  padding: 2rem 1.5rem; width: 100%; max-width: 360px;
  display: flex; flex-direction: column; gap: 1rem; text-align: center;
}
.login-card form { display: flex; flex-direction: column; gap: 0.75rem; }
.login-mascot { width: 160px; height: auto; display: block; margin: 0 auto; border-radius: 28px; }
.login-card h1 { font-family: var(--font-display); font-size: 1.75rem; font-weight: 700; letter-spacing: -0.02em; }
.login-subtitle { font-size: 0.9375rem; color: var(--text-2); }
.login-input {
  width: 100%; min-height: 48px; padding: 0 1rem;
  border: 1px solid var(--border); border-radius: var(--radius-md);
  font-size: 1rem; background: var(--surface);
  transition: border-color var(--ease), box-shadow var(--ease);
}
.login-input:focus { outline: none; border-color: var(--accent); box-shadow: 0 0 0 3px var(--accent-soft); }
.login-input::placeholder, .picker-search input::placeholder,
.edit-sheet-field input::placeholder { color: var(--text-2); }
.login-btn { width: 100%; }

/* ===== Offline banner ===== */
.offline-banner {
  position: fixed; bottom: 0; left: 0; right: 0;
  background: var(--text); color: var(--bg);
  text-align: center; padding: 0.6rem; font-size: 0.875rem; z-index: 300;
  /* push above home-indicator on iPhone */
  padding-bottom: max(0.6rem, env(safe-area-inset-bottom));
}

/* ===== Error message ===== */
.error-msg {
  background: var(--danger-soft); color: var(--danger);
  padding: 0.75rem 1rem; border-radius: var(--radius-md);
  font-size: 0.9375rem; text-align: center; margin: 0.5rem 0;
}

/* ===== Bottom sheets & modals (section picker, edit card) ===== */
.sheet-backdrop,
#edit-sheet-backdrop {
  position: fixed; inset: 0;
  background: rgba(0, 0, 0, 0.4);
  display: flex; align-items: flex-end; justify-content: center;
  z-index: 150;
  opacity: 0; pointer-events: none;
  transition: opacity 0.2s ease;
}
.sheet-backdrop.open,
#edit-sheet-backdrop.open { opacity: 1; pointer-events: auto; }

.sheet,
#edit-sheet {
  background: var(--surface);
  border-radius: var(--radius-lg) var(--radius-lg) 0 0;
  padding: 0.75rem 1rem;
  padding-bottom: max(1rem, env(safe-area-inset-bottom));
  width: 100%; max-width: 640px; max-height: 100%;
  overflow-y: auto;
  transform: translateY(100%);
  transition: transform 0.28s cubic-bezier(0.32, 0.72, 0, 1);
}
.sheet-backdrop.open .sheet,
#edit-sheet-backdrop.open #edit-sheet { transform: translateY(0); }
.sheet:focus { outline: none; }

.sheet-handle, .edit-sheet-handle {
  width: 2.5rem; height: 4px; background: var(--silver);
  border-radius: 2px; margin: 0 auto 0.75rem;
}

/* Section picker */
.sheet { display: flex; flex-direction: column; height: 85dvh; overflow: hidden; }
.picker-head { display: flex; align-items: center; justify-content: space-between; }
.picker-head h3 { font-family: var(--font-display); font-size: 1.0625rem; font-weight: 600; }
.picker-head .btn-icon { margin-right: -0.5rem; font-size: 1rem; }
.picker-search { padding: 0.5rem 0 0.75rem; }
.picker-search input {
  width: 100%; min-height: 44px; padding: 0 0.875rem;
  background: var(--fill); border: 2px solid transparent; border-radius: var(--radius-md);
  font-size: 1rem; /* 16px avoids iOS zoom on focus */
  transition: border-color var(--ease), background var(--ease);
}
.picker-search input:focus { outline: none; border-color: var(--accent); background: var(--surface); }
.picker-list { list-style: none; flex: 1; overflow-y: auto; overscroll-behavior: contain; margin: 0 -0.5rem; padding: 0 0.5rem; }
.picker-option {
  display: flex; align-items: center; gap: 0.75rem; min-height: 48px;
  padding: 0.5rem 0.75rem; border-radius: var(--radius-sm); cursor: pointer;
  transition: background var(--ease);
}
.picker-option:hover, .picker-option.kbd-active { background: var(--fill); }
.picker-option.kbd-active { outline: 2px solid var(--accent); outline-offset: -2px; }
.picker-option[aria-selected="true"] { background: var(--accent-soft); font-weight: 600; }
.picker-check { width: 1.1rem; flex-shrink: 0; color: var(--accent-text); font-weight: 700; }
.picker-name { flex: 1; min-width: 0; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.picker-date { flex-shrink: 0; font-size: 0.8125rem; color: var(--text-2); font-variant-numeric: tabular-nums; }
.picker-empty { text-align: center; color: var(--text-2); padding: 2rem 0; }

/* Edit card sheet */
#edit-sheet h3 { font-family: var(--font-display); font-size: 1.0625rem; font-weight: 600; margin-bottom: 1rem; }
.edit-sheet-field { display: flex; flex-direction: column; gap: 0.3rem; margin-bottom: 0.875rem; }
.edit-sheet-field label {
  font-size: 0.75rem; font-weight: 600; text-transform: uppercase;
  letter-spacing: 0.08em; color: var(--text-2);
}
.edit-sheet-field input,
.edit-sheet-field textarea {
  border: 1px solid var(--border); border-radius: var(--radius-md);
  padding: 0.65rem 0.875rem; font-size: 1rem; resize: vertical; outline: none;
  background: var(--bg);
  transition: border-color var(--ease), box-shadow var(--ease), background var(--ease);
}
.edit-sheet-field input:focus,
.edit-sheet-field textarea:focus {
  border-color: var(--accent); background: var(--surface); box-shadow: 0 0 0 3px var(--accent-soft);
}
.edit-sheet-field textarea { min-height: 3.5rem; }
.edit-error { color: var(--danger); font-size: 0.875rem; margin: 0.25rem 0 0.5rem; }
.edit-sheet-actions {
  display: flex; gap: 0.75rem; margin-top: 1rem; position: sticky; bottom: 0;
  background: var(--surface); padding-bottom: max(0.5rem, env(safe-area-inset-bottom));
}
.edit-sheet-actions button { flex: 1; }
#edit-cancel {
  background: var(--fill); border: none; border-radius: 999px; min-height: 44px;
  padding: 0.75rem 1rem; font-size: 1rem; font-weight: 500; cursor: pointer;
  transition: background var(--ease);
}
#edit-cancel:hover { background: var(--fill-hover); }
.edit-sheet-delete { display: block; width: 100%; margin-top: 0.75rem; font-size: 1rem; }

/* Pinyin sits at the top of the card back, centered, above a divider and the
   rest of the card. */
.card-pinyin-block {
  margin-bottom: 1rem; padding-bottom: 0.75rem;
  border-bottom: 1px solid var(--border); text-align: center; width: 100%;
}
.card-pinyin { font-weight: 700; font-size: 1.125rem; }
/* Tone colors: 1 red, 2 green, 3 blue, 4 purple, 5 neutral gray */
.tone-1 { color: #c0392b; }
.tone-2 { color: #1e8449; }
.tone-3 { color: #2471a3; }
.tone-4 { color: #7d3c98; }
.tone-5 { color: var(--text-2); }
@media (prefers-color-scheme: dark) {
  .tone-1 { color: #ff7b6e; }
  .tone-2 { color: #4cd47e; }
  .tone-3 { color: #5eb3f0; }
  .tone-4 { color: #c58be0; }
}

/* ===== Landscape phones: reduce heights so nothing overflows ===== */
@media (max-height: 500px) and (orientation: landscape) {
  .home-main { padding-top: 1rem; gap: 1rem; }
  .centered { min-height: 40vh; }
  .sheet { height: 100dvh; border-radius: 0; }
}

/* ===== Small phones ===== */
@media (max-width: 359px) {
  .greeting h2 { font-size: 1.5rem; }
  .hero-count { font-size: 2.125rem; }
}

/* ===== ≥640px: section picker becomes a centered modal ===== */
@media (min-width: 640px) {
  .sheet-backdrop { align-items: center; }
  .sheet {
    border-radius: var(--radius-lg); height: min(560px, 80dvh); max-width: 480px;
    box-shadow: var(--shadow-pop); transform: translateY(12px) scale(0.98);
  }
  .sheet-handle { display: none; }
  .sheet-backdrop.open .sheet { transform: none; }
}

/* ===== ≥768px: centered content column ===== */
@media (min-width: 768px) {
  .view { max-width: var(--column); margin: 0 auto; }
  .app-header { padding: 0 1.5rem; height: 64px; }
  .home-main { padding: 1.5rem 1.5rem 3rem; gap: 2rem; }
  .greeting h2 { font-size: 2rem; }
  .hero { padding: 2rem; }
  .btn-cta { width: auto; min-width: 220px; }
  .metric-number { font-size: 1.75rem; }
  .browse-main { padding: 1.5rem; }
  .flashcard-scene { height: 320px; }
  .card-word { font-size: 2.75rem; }

  .offline-banner {
    max-width: var(--column);
    left: 50%; right: auto; width: 100%;
    transform: translateX(-50%);
    border-radius: 0.5rem 0.5rem 0 0;
  }
}

/* ===== Reduced motion ===== */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    transition-duration: 0.01ms !important;
    animation-duration: 0.01ms !important;
  }
}

/* ===== Audio ===== */
.card-speak-row { display: flex; justify-content: center; margin: 1rem 0 0; min-height: 0; }
.btn-speak { flex-shrink: 0; font-size: 1.125rem; }
.voice-status { margin-top: 0.25rem; color: var(--danger); }
#study-notice { color: var(--text-2); }

/* ===== Quiz ===== */
#quiz-area { width: 100%; max-width: 440px; margin: 0 auto; display: flex; flex-direction: column; gap: 1.25rem; }
.quiz-prompt {
  display: flex; flex-direction: column; align-items: center; gap: 0.5rem; text-align: center;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-lg);
  padding: 1.5rem 1rem;
}
.quiz-label { font-size: 0.8125rem; text-transform: uppercase; letter-spacing: 0.08em; color: var(--text-2); }
.quiz-hanzi {
  font-family: var(--font-display); font-size: 3rem; font-weight: 700; line-height: 1.2;
  word-break: break-word; overflow-wrap: anywhere;
}
.quiz-hanzi-sm { font-size: 2.25rem; }
.quiz-meaning { font-size: 1.5rem; font-weight: 600; }
.quiz-pinyin { font-size: 1.25rem; font-weight: 600; }
.quiz-play { min-height: 56px; font-size: 1.0625rem; }
.quiz-options { display: grid; grid-template-columns: 1fr; gap: 0.5rem; }
.quiz-option {
  display: flex; align-items: center; gap: 0.75rem; text-align: left;
  min-height: 56px; padding: 0.75rem 1rem; font-size: 1.0625rem;
  background: var(--surface); color: var(--text);
  border: 1.5px solid var(--border); border-radius: var(--radius-md); cursor: pointer;
  transition: border-color var(--ease), background var(--ease), transform var(--ease);
}
.quiz-option:not(:disabled):hover { background: var(--fill); }
.quiz-option:not(:disabled):active { transform: scale(0.98); }
.quiz-option:disabled { cursor: default; }
.quiz-option-hanzi { font-family: var(--font-display); font-size: 1.5rem; font-weight: 700; }
.quiz-key {
  flex-shrink: 0; width: 1.5rem; height: 1.5rem; border-radius: 50%;
  display: grid; place-items: center; background: var(--fill);
  font-family: var(--font-text); font-size: 0.8125rem; font-weight: 600; color: var(--text-2);
}
/* Right / wrong carry an icon as well as colour */
.quiz-option.right { border-color: #1e8449; background: rgba(30, 132, 73, 0.14); }
.quiz-option.wrong { border-color: var(--danger); background: var(--danger-soft); }
.quiz-option.right .quiz-key::before { content: "✓"; }
.quiz-option.wrong .quiz-key::before { content: "✗"; }
.quiz-option.right .quiz-key, .quiz-option.wrong .quiz-key { font-size: 0; }
.quiz-option.right .quiz-key::before, .quiz-option.wrong .quiz-key::before { font-size: 0.8125rem; }
.quiz-result { display: flex; flex-direction: column; align-items: center; gap: 0.375rem; text-align: center; }
.quiz-result:empty { display: none; }
.quiz-verdict { font-size: 1.125rem; font-weight: 700; }
.quiz-verdict.ok { color: #1e8449; }
.quiz-verdict.no { color: var(--danger); }
.quiz-english { font-size: 1.0625rem; }

.quiz-actions { display: flex; gap: 0.5rem; width: 100%; margin-top: 0.75rem; }
.quiz-actions .btn { flex: 1; }
@media (prefers-color-scheme: dark) {
  .quiz-option.right { border-color: #4cd47e; background: rgba(76, 212, 126, 0.16); }
  .quiz-verdict.ok { color: #4cd47e; }
}
@media (hover: none) { .quiz-key { display: none; } }

/* ===== Example sentence: hanzi / pinyin / English ===== */
.ex-block { display: flex; flex-direction: column; gap: 0.125rem; font-style: normal; text-align: center; }
.ex-zh { font-size: 1.125rem; font-weight: 500; white-space: pre-line; }
.ex-py { font-size: 0.9375rem; color: var(--text-2); }
.ex-en { font-size: 0.9375rem; }
.word-detail .ex-block { text-align: left; margin: 0 0 0.75rem; }
.quiz-stop { align-self: center; min-height: 44px; color: var(--text-2); font-size: 0.9375rem; }