:root {
  --bg: #FFF0F5;
  --card-bg: #FFFFFF;
  --border: #FFB6C1;
  --primary: #FF8FAB;
  --primary-dark: #F4728F;
  --word-text: #4A3B42;
  --sub-text: #C48B9F;
  --meaning-text: #666666;
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  background: var(--bg);
  color: var(--word-text);
  padding-bottom: 160px;
}

.topbar {
  position: sticky;
  top: 0;
  z-index: 10;
  background: var(--card-bg);
  border-bottom: 1px solid var(--border);
}

.book-title {
  font-size: 22px;
  font-weight: 600;
  color: var(--word-text);
  text-align: center;
  padding: 14px 16px 4px;
}

.unit-nav {
  display: flex;
  gap: 8px;
  overflow-x: auto;
  padding: 8px 16px 10px;
  -webkit-overflow-scrolling: touch;
}

.unit-chip {
  flex: 0 0 auto;
  border: 1px solid var(--border);
  background: var(--card-bg);
  color: var(--sub-text);
  border-radius: 999px;
  padding: 6px 14px;
  font-size: 14px;
  font-family: inherit;
  white-space: nowrap;
  cursor: pointer;
  transition: background .2s, color .2s;
}

.unit-chip:active {
  background: var(--primary);
  color: #FFFFFF;
  border-color: var(--primary);
}

.word-list {
  max-width: 720px;
  margin: 0 auto;
  padding: 8px 16px;
}

.unit-name {
  font-size: 18px;
  font-weight: 600;
  color: var(--primary-dark);
  border-left: 4px solid var(--primary);
  padding-left: 10px;
  margin: 18px 0 10px;
}

.cards {
  display: grid;
  grid-template-columns: 1fr;
  gap: 10px;
}

@media (min-width: 560px) {
  .cards {
    grid-template-columns: 1fr 1fr;
  }
}

.word-card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 12px 14px;
  text-align: center;
  cursor: pointer;
  transition: box-shadow .2s, transform .1s;
}

.word-card:active {
  transform: scale(.98);
}

.word-card.current {
  border-color: var(--primary);
  box-shadow: 0 0 0 2px var(--primary);
}

.card-en {
  display: block;
  font-size: 22px;
  font-weight: 600;
  color: var(--word-text);
  word-break: break-word;
}

.card-phonetic {
  display: block;
  font-size: 14px;
  color: var(--sub-text);
  margin-top: 2px;
  min-height: 18px;
}

.card-zh {
  display: block;
  font-size: 14px;
  color: var(--meaning-text);
  margin-top: 4px;
  line-height: 1.5;
}

.control-bar {
  position: fixed;
  left: 0;
  right: 0;
  bottom: 0;
  z-index: 10;
  background: var(--card-bg);
  border-top: 1px solid var(--border);
  padding: 10px 16px calc(10px + env(safe-area-inset-bottom));
}

.ctrl-row {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 12px;
  max-width: 720px;
  margin: 0 auto;
}

.ctrl-btn {
  border: 1px solid var(--border);
  background: var(--card-bg);
  color: var(--primary-dark);
  border-radius: 999px;
  padding: 10px 20px;
  font-size: 15px;
  font-family: inherit;
  cursor: pointer;
  transition: background .2s, color .2s;
}

.ctrl-btn:hover {
  background: #FFF0F5;
}

.ctrl-btn:active {
  background: var(--primary);
  color: #FFFFFF;
  border-color: var(--primary);
}

.play-btn {
  background: var(--primary);
  border-color: var(--primary);
  color: #FFFFFF;
  min-width: 96px;
}

.play-btn:hover {
  background: var(--primary-dark);
  border-color: var(--primary-dark);
}

.play-btn:active {
  background: var(--primary-dark);
  border-color: var(--primary-dark);
}

.sub-row {
  margin-top: 8px;
  gap: 16px;
}

.sub-ctl {
  font-size: 13px;
  color: var(--meaning-text);
  display: flex;
  align-items: center;
  gap: 4px;
}

.interval-input {
  width: 52px;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 4px 6px;
  font-size: 13px;
  font-family: inherit;
  text-align: center;
  color: var(--word-text);
  background: var(--card-bg);
}

.progress {
  font-size: 13px;
  color: var(--sub-text);
  margin-left: auto;
}

.status-msg {
  text-align: center;
  font-size: 12px;
  color: var(--primary-dark);
  min-height: 16px;
  margin-top: 4px;
}