:root {
  --bg: #f5f7fb;
  --card-bg: #ffffff;
  --primary: #2563eb;
  --primary-soft: #dbeafe;
  --danger: #dc2626;
  --success: #16a34a;
  --text-main: #111827;
  --text-muted: #6b7280;
  --border: #e5e7eb;
  --radius-lg: 16px;
  --radius-md: 10px;
  --shadow-soft: 0 12px 30px rgba(15, 23, 42, 0.06);
}

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

body {
  margin: 0;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "SF Pro Text",
    "PingFang SC", "Microsoft Yahei", sans-serif;
  background: radial-gradient(circle at top left, #eff6ff, #f9fafb);
  color: var(--text-main);
}

.app {
  max-width: 960px;
  margin: 24px auto;
  padding: 12px;
}

.app-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 12px;
  padding: 16px 20px;
  background: var(--card-bg);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-soft);
}

.title-area h1 {
  margin: 0;
  font-size: 24px;
}

.subtitle {
  margin: 4px 0 0;
  font-size: 13px;
  color: var(--text-muted);
}

.stats {
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  font-size: 13px;
  color: var(--text-muted);
  gap: 2px;
}

.mode-tabs {
  display: flex;
  gap: 8px;
  margin: 12px 0 16px;
  flex-wrap: wrap;
}

.mode-tab {
  padding: 8px 12px;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: var(--card-bg);
  color: var(--text-muted);
  font-size: 13px;
  cursor: pointer;
  transition: all 0.15s ease;
}

.mode-tab:hover {
  border-color: var(--primary);
}

.mode-tab.active {
  background: var(--primary-soft);
  border-color: var(--primary);
  color: var(--primary);
}

.main-panel {
  display: grid;
  grid-template-columns: minmax(0, 0.9fr) minmax(0, 1.1fr);
  gap: 16px;
}

@media (max-width: 768px) {
  .main-panel {
    grid-template-columns: 1fr;
  }
}

.sentence-panel,
.practice-panel {
  background: var(--card-bg);
  border-radius: var(--radius-lg);
  padding: 16px 18px;
  box-shadow: var(--shadow-soft);
}

.sentence-panel h2 {
  margin-top: 0;
  font-size: 16px;
}

.zh-sentence {
  margin: 10px 0 0;
  font-size: 18px;
  font-weight: 500;
}

.mode-label {
  font-size: 13px;
  color: var(--text-muted);
  margin-bottom: 10px;
}

.workspace {
  min-height: 80px;
  padding: 10px;
  border-radius: var(--radius-md);
  background: #f9fafb;
  border: 1px dashed var(--border);
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  align-items: center;
}

.answer-preview {
  min-height: 24px;
  margin-top: 10px;
  font-size: 14px;
  color: var(--text-muted);
}

.token-btn {
  padding: 6px 10px;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: #ffffff;
  font-size: 14px;
  cursor: pointer;
  box-shadow: 0 2px 4px rgba(148, 163, 184, 0.3);
  transition: transform 0.12s ease, box-shadow 0.12s ease, background 0.12s ease;
}

.token-btn:hover {
  transform: translateY(-1px);
  box-shadow: 0 4px 8px rgba(148, 163, 184, 0.4);
}

.token-btn.used {
  background: #e5e7eb;
  color: var(--text-muted);
  box-shadow: none;
}

.gap-input,
.text-input {
  width: 100%;
  padding: 8px 10px;
  border-radius: var(--radius-md);
  border: 1px solid var(--border);
  font-size: 15px;
}

.gap-label {
  font-size: 14px;
  margin-bottom: 6px;
}

.controls {
  margin-top: 12px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 8px;
}

.controls-right {
  display: flex;
  gap: 8px;
}

button {
  font-family: inherit;
}

.primary {
  background: var(--primary);
  color: #fff;
  border-radius: 999px;
  border: none;
  padding: 8px 16px;
  font-size: 14px;
  cursor: pointer;
  box-shadow: 0 4px 10px rgba(37, 99, 235, 0.4);
  transition: transform 0.1s ease, box-shadow 0.1s ease, opacity 0.1s ease;
}

.primary:hover {
  transform: translateY(-1px);
  box-shadow: 0 6px 16px rgba(37, 99, 235, 0.5);
}

.primary:active {
  transform: translateY(0);
  box-shadow: 0 3px 8px rgba(37, 99, 235, 0.4);
}

#next-btn,
#speak-btn {
  background: #ffffff;
  border-radius: 999px;
  border: 1px solid var(--border);
  padding: 8px 14px;
  font-size: 14px;
  cursor: pointer;
}

.feedback {
  min-height: 20px;
  margin: 10px 0 0;
  font-size: 14px;
}

.feedback.ok {
  color: var(--success);
}

.feedback.bad {
  color: var(--danger);
}

.hint {
  margin-top: 6px;
  font-size: 12px;
  color: var(--text-muted);
}