:root {
  --bg: #f4f7fb;
  --card-bg: #ffffff;
  --primary: #4a7cff;
  --primary-dark: #2f5ed9;
  --secondary: #eef3ff;
  --success: #1fa671;
  --warning: #f59b3b;
  --text: #1d2433;
  --muted: #6f7b8d;
  --border: #e4eaf5;
  --shadow: 0 10px 30px rgba(33, 64, 120, 0.12);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: "Segoe UI", Arial, "PingFang SC", "Microsoft YaHei", sans-serif;
  background: linear-gradient(135deg, #eef5ff 0%, #f8f9ff 100%);
  color: var(--text);
}

.container {
  max-width: 760px;
  margin: 48px auto;
  padding: 20px;
}

.upload-panel {
  margin-bottom: 22px;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 12px;
  flex-wrap: wrap;
  padding: 18px 20px;
  background: rgba(255, 255, 255, 0.8);
  border: 2px dashed #c9d6ff;
  border-radius: 18px;
  transition: all 0.2s ease;
}

.drop-zone.dragover {
  border-color: var(--primary);
  background: #edf4ff;
  transform: translateY(-1px);
}

.file-label {
  display: inline-block;
  padding: 10px 18px;
  background: var(--primary);
  color: white;
  border-radius: 12px;
  font-weight: 600;
  cursor: pointer;
  box-shadow: var(--shadow);
}

.drop-hint {
  color: var(--muted);
  font-size: 0.95rem;
}

input[type="file"] {
  display: none;
}

.toolbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 18px;
}

.toggle-wrap {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  background: rgba(255, 255, 255, 0.7);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 10px 14px;
  font-weight: 600;
}

.toggle-wrap input {
  width: 18px;
  height: 18px;
}

.ghost-btn {
  background: #f1f4ff;
  color: var(--primary-dark);
}

.stats-panel {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
  margin-bottom: 22px;
}

.stat-box {
  background: rgba(255, 255, 255, 0.8);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 14px 16px;
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.stat-label {
  color: var(--muted);
  font-size: 0.82rem;
}

#progressStats,
#accuracyStats {
  font-size: 1.3rem;
  font-weight: 700;
}

.card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 20px;
  box-shadow: var(--shadow);
  padding: 24px 22px;
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 24px;
}

#progressText {
  font-size: 0.95rem;
  color: var(--muted);
  font-weight: 600;
}

.nav-buttons {
  display: flex;
  gap: 12px;
}

button {
  border: none;
  border-radius: 12px;
  padding: 10px 16px;
  font-size: 1rem;
  cursor: pointer;
  transition: transform 0.18s ease, opacity 0.18s ease;
}

button:hover {
  transform: translateY(-1px);
}

button:active {
  transform: translateY(0);
}

button:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

#prevBtn,
#nextBtn {
  background: var(--secondary);
  color: var(--text);
}

.primary-btn {
  background: var(--primary);
  color: #fff;
  flex: 1;
}

.secondary-btn {
  background: #edf2ff;
  color: var(--primary-dark);
  flex: 1;
}

.success-btn {
  background: rgba(31, 166, 113, 0.14);
  color: var(--success);
  flex: 1;
}

.warn-btn {
  background: rgba(245, 155, 59, 0.14);
  color: #b76a09;
  flex: 1;
}

.word-block {
  text-align: center;
  padding: 18px 10px 10px;
}

.word {
  font-size: clamp(2.4rem, 6vw, 4rem);
  font-weight: 800;
  letter-spacing: 0.04em;
  margin-bottom: 10px;
}

.phonetic {
  font-size: 1.4rem;
  color: var(--muted);
  min-height: 2rem;
}

.action-row,
.answer-row {
  display: flex;
  gap: 14px;
  margin-top: 24px;
}

.answer-row {
  margin-top: 14px;
}

.translation {
  margin-top: 22px;
  font-size: 1.2rem;
  line-height: 1.6;
  background: #f7f9ff;
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 16px 18px;
  color: var(--text);
}

.hidden {
  display: none;
}

@media (max-width: 600px) {
  .container {
    margin: 24px auto;
    padding: 14px;
  }

  .topbar,
  .action-row,
  .answer-row,
  .toolbar {
    flex-direction: column;
    align-items: stretch;
  }

  .nav-buttons {
    width: 100%;
  }

  .nav-buttons button,
  .action-row button,
  .answer-row button,
  .ghost-btn,
  .toggle-wrap {
    width: 100%;
  }

  .stats-panel {
    grid-template-columns: 1fr;
  }
}