:root {
  --bg-0: #f5f5f7;
  --bg-1: #e8ecf4;
  --bg-2: #dfe7f3;
  --text: #1d1d1f;
  --text-muted: #6e6e73;
  --text-soft: #86868b;
  --accent: #007aff;
  --accent-2: #5856d6;
  --success: #34c759;
  --error: #ff3b30;
  --glass: rgba(255, 255, 255, 0.72);
  --glass-strong: rgba(255, 255, 255, 0.88);
  --glass-border: rgba(255, 255, 255, 0.65);
  --glass-shadow: 0 8px 32px rgba(0, 0, 0, 0.08), 0 2px 8px rgba(0, 0, 0, 0.04);
  --glass-inset: inset 0 1px 0 rgba(255, 255, 255, 0.9);
  --radius: 20px;
  --radius-sm: 14px;
  --radius-pill: 999px;
  --font: -apple-system, BlinkMacSystemFont, "Inter", "Noto Sans SC", "Segoe UI", sans-serif;
  --topbar-h: 64px;
  --max-w: 520px;
}

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

html {
  -webkit-font-smoothing: antialiased;
  -webkit-tap-highlight-color: transparent;
}

body {
  font-family: var(--font);
  color: var(--text);
  line-height: 1.5;
  min-height: 100dvh;
  background: var(--bg-0);
}

.bg-mesh {
  position: fixed;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  background:
    radial-gradient(ellipse 70% 50% at 20% 10%, rgba(0, 122, 255, 0.12), transparent 55%),
    radial-gradient(ellipse 60% 45% at 85% 20%, rgba(88, 86, 214, 0.1), transparent 50%),
    radial-gradient(ellipse 50% 40% at 50% 100%, rgba(52, 199, 89, 0.08), transparent 50%),
    linear-gradient(165deg, var(--bg-0) 0%, var(--bg-1) 45%, var(--bg-2) 100%);
}

.hidden {
  display: none !important;
}

/* ── Glass primitives ── */
.glass {
  background: var(--glass);
  backdrop-filter: blur(24px) saturate(180%);
  -webkit-backdrop-filter: blur(24px) saturate(180%);
  border: 1px solid var(--glass-border);
  box-shadow: var(--glass-shadow), var(--glass-inset);
}

.glass-inset {
  background: rgba(255, 255, 255, 0.45);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid rgba(255, 255, 255, 0.55);
  border-radius: var(--radius-sm);
  box-shadow: inset 0 1px 2px rgba(255, 255, 255, 0.8);
}

.glass-input {
  width: 100%;
  padding: 0.7rem 1rem;
  font: inherit;
  font-size: 16px;
  color: var(--text);
  background: rgba(255, 255, 255, 0.55);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid rgba(255, 255, 255, 0.7);
  border-radius: var(--radius-sm);
  box-shadow: inset 0 1px 2px rgba(0, 0, 0, 0.04);
  transition: border-color 0.2s, box-shadow 0.2s;
}

.glass-input:focus {
  outline: none;
  border-color: rgba(0, 122, 255, 0.45);
  box-shadow: 0 0 0 4px rgba(0, 122, 255, 0.15), inset 0 1px 2px rgba(0, 0, 0, 0.04);
}

.glass-btn {
  background: rgba(255, 255, 255, 0.6);
  backdrop-filter: blur(16px) saturate(160%);
  -webkit-backdrop-filter: blur(16px) saturate(160%);
  border: 1px solid rgba(255, 255, 255, 0.75);
  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.06), inset 0 1px 0 rgba(255, 255, 255, 0.9);
  transition: transform 0.15s, box-shadow 0.2s, background 0.2s;
}

.glass-btn:hover {
  background: rgba(255, 255, 255, 0.85);
  transform: translateY(-1px);
  box-shadow: 0 6px 20px rgba(0, 0, 0, 0.08), inset 0 1px 0 rgba(255, 255, 255, 1);
}

.glass-btn:active {
  transform: translateY(0);
  background: rgba(255, 255, 255, 0.6);
}

.glass-btn:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.glass-btn:focus:not(.btn-primary) {
  background: rgba(255, 255, 255, 0.6);
}

.glass-btn.btn-primary:hover,
.glass-btn.btn-primary:focus,
.glass-btn.btn-primary:active {
  background: linear-gradient(135deg, rgba(0, 122, 255, 0.9), rgba(88, 86, 214, 0.85));
}

/* ── App shell ── */
.app {
  position: relative;
  z-index: 1;
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 0 1rem 2.5rem;
  min-height: 100dvh;
}

.topbar {
  position: sticky;
  top: 0.75rem;
  z-index: 100;
  display: flex;
  align-items: center;
  gap: 0.65rem;
  min-height: var(--topbar-h);
  margin-bottom: 1rem;
  padding: 0.5rem 0.75rem;
  border-radius: var(--radius);
}

.back-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.2rem;
  padding: 0.45rem 0.85rem;
  border-radius: var(--radius-pill);
  font-size: 0.85rem;
  font-weight: 500;
  cursor: pointer;
  color: var(--text);
  flex-shrink: 0;
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.65rem;
  flex: 1;
  min-width: 0;
}

.brand-icon {
  width: 40px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 12px;
  font-weight: 700;
  font-size: 0.85rem;
  color: var(--accent);
}

.brand-title {
  font-size: 1.05rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.brand-sub {
  font-size: 0.72rem;
  color: var(--text-muted);
}

.topbar-title {
  font-size: 1rem;
  font-weight: 600;
  flex: 1;
  text-align: center;
}

/* ── Views ── */
.view {
  display: none;
  animation: rise 0.35s cubic-bezier(0.22, 1, 0.36, 1);
}

.view--active {
  display: block;
}

@keyframes rise {
  from {
    opacity: 0;
    transform: translateY(12px);
  }
  to {
    opacity: 1;
    transform: none;
  }
}

.panel {
  padding: 1.25rem;
  border-radius: var(--radius);
  margin-bottom: 1rem;
}

.hero {
  padding: 1.5rem 1.25rem;
  border-radius: var(--radius);
  margin-bottom: 1.25rem;
  text-align: center;
}

.hero-greet {
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--accent);
  letter-spacing: 0.06em;
  text-transform: uppercase;
  margin-bottom: 0.35rem;
}

.hero-heading {
  font-size: 1.4rem;
  font-weight: 700;
  letter-spacing: -0.03em;
}

.hero-meta {
  margin-top: 0.5rem;
  font-size: 0.85rem;
  color: var(--text-muted);
}

.hero-meta strong {
  color: var(--text);
}

/* ── Feature grid ── */
.feature-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 0.75rem;
}

.feature-card {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  text-align: left;
  padding: 1.15rem;
  border-radius: var(--radius);
  cursor: pointer;
  color: inherit;
  transition: transform 0.2s cubic-bezier(0.22, 1, 0.36, 1);
}

.feature-card:hover {
  transform: scale(1.02);
}

.feature-card:active {
  transform: scale(0.98);
}

.feature-icon {
  font-size: 1.6rem;
  margin-bottom: 0.5rem;
}

.feature-name {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 0.15rem;
}

.feature-desc {
  font-size: 0.75rem;
  color: var(--text-muted);
  line-height: 1.35;
}

/* ── Group bar ── */
.group-bar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.5rem;
  margin-bottom: 1rem;
}

.group-label {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--text-muted);
  white-space: nowrap;
}

.group-select {
  flex: 1;
  min-width: 140px;
  cursor: pointer;
}

/* ── Buttons ── */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.65rem 1.2rem;
  font: inherit;
  font-size: 0.9rem;
  font-weight: 600;
  border: none;
  border-radius: var(--radius-pill);
  cursor: pointer;
  color: var(--text);
}

.btn-primary {
  background: linear-gradient(135deg, rgba(0, 122, 255, 0.9), rgba(88, 86, 214, 0.85));
  color: #fff;
  border: 1px solid rgba(255, 255, 255, 0.35);
  box-shadow: 0 4px 16px rgba(0, 122, 255, 0.35), inset 0 1px 0 rgba(255, 255, 255, 0.35);
}

.btn-primary:hover {
  box-shadow: 0 8px 24px rgba(0, 122, 255, 0.4), inset 0 1px 0 rgba(255, 255, 255, 0.4);
}

.btn-lg {
  width: 100%;
  padding: 0.85rem;
  margin-top: 0.75rem;
  font-size: 1rem;
}

.btn-sm {
  padding: 0.4rem 0.75rem;
  font-size: 0.8rem;
}

.hint {
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-top: 0.35rem;
}

.msg {
  font-size: 0.9rem;
  margin-top: 0.75rem;
  padding: 0.65rem 0.85rem;
  border-radius: var(--radius-sm);
}

.msg--success {
  color: #1a7f37;
  background: rgba(52, 199, 89, 0.15);
}

.msg--error {
  color: var(--error);
  background: rgba(255, 59, 48, 0.1);
}

/* ── Word card (memorize) ── */
.word-card {
  padding: 1.35rem;
  border-radius: var(--radius);
  margin-bottom: 1rem;
}

.word-card-head {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 0.75rem;
  margin-bottom: 0.75rem;
}

.word-card-word {
  font-size: 2rem;
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.15;
}

.word-card-phonetic {
  font-size: 1rem;
  color: var(--accent);
  margin-top: 0.25rem;
  font-weight: 500;
}

.word-card-zh {
  font-size: 1.2rem;
  font-weight: 600;
  color: var(--text);
  margin-bottom: 1rem;
  padding-bottom: 0.85rem;
  border-bottom: 1px solid rgba(0, 0, 0, 0.06);
}

.word-card-example {
  padding: 1rem;
}

.ex-label {
  font-size: 0.7rem;
  font-weight: 600;
  color: var(--text-soft);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 0.5rem;
}

.ex-en {
  font-size: 0.95rem;
  line-height: 1.55;
  margin-bottom: 0.5rem;
}

.ex-zh {
  font-size: 0.9rem;
  color: var(--text-muted);
  line-height: 1.5;
}

.speak-btn {
  width: 48px;
  height: 48px;
  border-radius: 50%;
  font-size: 1.25rem;
  cursor: pointer;
  flex-shrink: 0;
  display: flex;
  align-items: center;
  justify-content: center;
}

.speak-btn--lg {
  width: 56px;
  height: 56px;
  font-size: 1.4rem;
}

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

.card-progress {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-muted);
}

.card-extra {
  text-align: center;
  margin-top: 0.85rem;
}

/* ── Lookup ── */
.search-bar {
  display: flex;
  gap: 0.5rem;
}

.search-bar .glass-input {
  flex: 1;
}

.lookup-result {
  margin-top: 1rem;
  padding: 1.15rem;
  border-radius: var(--radius-sm);
}

.lookup-word {
  font-size: 1.75rem;
  font-weight: 700;
}

.lookup-phonetic {
  color: var(--accent);
  margin: 0.25rem 0 0.75rem;
}

.lookup-zh {
  font-size: 1.15rem;
  font-weight: 600;
  margin-bottom: 0.75rem;
}

.lookup-ex {
  padding: 0.85rem;
  margin: 0.75rem 0;
}

.lookup-actions {
  margin-top: 1rem;
}

/* ── Practice ── */
.quiz-progress {
  display: flex;
  justify-content: space-between;
  padding: 0.6rem 1rem;
  margin-bottom: 1rem;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-muted);
}

.quiz-word-block {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.5rem;
  padding: 1.5rem 1rem;
  border-radius: var(--radius);
  margin-bottom: 1.25rem;
  text-align: center;
}

.quiz-word {
  font-size: 2.25rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.quiz-phonetic {
  font-size: 1rem;
  color: var(--accent);
}

.quiz-options {
  display: flex;
  flex-direction: column;
  gap: 0.55rem;
  margin-bottom: 1rem;
}

.quiz-option {
  width: 100%;
  padding: 1rem 1.1rem;
  text-align: left;
  font: inherit;
  font-size: 0.95rem;
  border-radius: var(--radius-sm);
  cursor: pointer;
  color: var(--text);
  background: rgba(255, 255, 255, 0.55);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid rgba(255, 255, 255, 0.7);
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.04), inset 0 1px 0 rgba(255, 255, 255, 0.85);
  transition: transform 0.15s, border-color 0.15s, background 0.15s;
}

.quiz-option:hover:not(:disabled) {
  transform: scale(1.01);
  border-color: rgba(0, 122, 255, 0.35);
}

.quiz-option.is-correct {
  border-color: var(--success);
  background: rgba(52, 199, 89, 0.18);
}

.quiz-option.is-wrong {
  border-color: var(--error);
  background: rgba(255, 59, 48, 0.12);
}

.quiz-option:disabled {
  cursor: default;
}

.quiz-nav-row {
  display: flex;
  justify-content: space-between;
  gap: 0.5rem;
}

.practice-done {
  text-align: center;
  padding: 1.5rem 0;
}

.practice-done h3 {
  font-size: 1.25rem;
  margin-bottom: 0.5rem;
}

/* ── Word list ── */
.word-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.word-list li {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 0.75rem;
  padding: 0.9rem 1rem;
  border-radius: var(--radius-sm);
  background: rgba(255, 255, 255, 0.5);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid rgba(255, 255, 255, 0.65);
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.04);
}

.word-list-main strong {
  display: block;
  font-size: 1rem;
}

.word-list-main span {
  font-size: 0.85rem;
  color: var(--text-muted);
}

.word-list-meta {
  font-size: 0.75rem;
  color: var(--text-soft);
  margin-top: 0.2rem;
}

.word-list-actions {
  display: flex;
  gap: 0.35rem;
  flex-shrink: 0;
}

.icon-btn {
  padding: 0.4rem 0.55rem;
  border-radius: 10px;
  font-size: 0.8rem;
  cursor: pointer;
  background: rgba(255, 255, 255, 0.6);
  border: 1px solid rgba(255, 255, 255, 0.8);
  box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.9);
}

.icon-btn--danger {
  color: var(--error);
}

.empty-state {
  text-align: center;
  padding: 2.5rem 1rem;
  color: var(--text-muted);
}

.empty-hint {
  font-size: 0.85rem;
  margin-top: 0.35rem;
}

/* ── Chat ── */
.view--chat.view--active {
  display: flex;
  flex-direction: column;
}

.chat-panel {
  flex: 1;
  display: flex;
  flex-direction: column;
  min-height: calc(100dvh - var(--topbar-h) - 4rem);
  border-radius: var(--radius);
  overflow: hidden;
}

.chat-messages {
  flex: 1;
  overflow-y: auto;
  padding: 1rem;
  display: flex;
  flex-direction: column;
  gap: 0.65rem;
}

.chat-bubble {
  max-width: 88%;
  padding: 0.75rem 1rem;
  border-radius: 18px;
  font-size: 0.92rem;
  line-height: 1.5;
  white-space: pre-wrap;
  word-break: break-word;
}

.chat-bubble--user {
  align-self: flex-end;
  background: linear-gradient(135deg, rgba(0, 122, 255, 0.92), rgba(88, 86, 214, 0.88));
  color: #fff;
  border-bottom-right-radius: 6px;
  box-shadow: 0 4px 16px rgba(0, 122, 255, 0.25);
}

.chat-bubble--ai {
  align-self: flex-start;
  border-bottom-left-radius: 6px;
}

.chat-bubble--error {
  color: var(--error);
  border-color: rgba(255, 59, 48, 0.3);
}

.chat-input-row {
  display: flex;
  gap: 0.5rem;
  padding: 0.75rem;
  border-top: 1px solid rgba(0, 0, 0, 0.05);
  background: rgba(255, 255, 255, 0.4);
}

.chat-input-row textarea {
  flex: 1;
  resize: none;
}

.chat-clear-row {
  display: flex;
  justify-content: center;
  padding: 0.4rem 0.75rem 0.75rem;
}

@media (min-width: 540px) {
  .feature-grid {
    grid-template-columns: repeat(3, 1fr);
  }
}