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

body {
  font-family: -apple-system, "Microsoft YaHei", "PingFang SC", sans-serif;
  background: #f0f4f8;
  min-height: 100vh;
  color: #333;
}

/* ======== Header ======== */
.site-header {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: #fff;
  padding: 2rem 1rem;
  text-align: center;
}

.site-header h1 {
  font-size: 2rem;
  font-weight: 800;
  letter-spacing: 2px;
}

.site-header p {
  margin-top: 0.5rem;
  opacity: 0.9;
  font-size: 1rem;
}

/* ======== Container ======== */
.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 2rem 1rem;
}

/* ======== Card Grid ======== */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1.5rem;
}

.card {
  background: #fff;
  border-radius: 16px;
  padding: 1.5rem;
  box-shadow: 0 4px 12px rgba(0,0,0,0.08);
  cursor: pointer;
  transition: transform 0.2s, box-shadow 0.2s;
  text-decoration: none;
  color: inherit;
  display: flex;
  flex-direction: column;
  position: relative;
  overflow: hidden;
}

.card:hover {
  transform: translateY(-4px);
  box-shadow: 0 8px 24px rgba(0,0,0,0.12);
}

.card .icon {
  font-size: 2.5rem;
  margin-bottom: 0.75rem;
}

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

.card p {
  font-size: 0.9rem;
  color: #666;
  line-height: 1.5;
  flex: 1;
}

.card .meta {
  margin-top: 1rem;
  display: flex;
  align-items: center;
  gap: 0.75rem;
  font-size: 0.8rem;
}

.badge {
  display: inline-block;
  padding: 0.2rem 0.6rem;
  border-radius: 999px;
  font-size: 0.75rem;
  font-weight: 600;
}

.badge-easy {
  background: #d4edda;
  color: #155724;
}

.badge-medium {
  background: #fff3cd;
  color: #856404;
}

.badge-hard {
  background: #f8d7da;
  color: #721c24;
}

.card .tag {
  display: inline-block;
  background: #e9ecef;
  color: #495057;
  padding: 0.15rem 0.5rem;
  border-radius: 4px;
  font-size: 0.7rem;
}

/* ======== Test Page ======== */
.test-page {
  max-width: 700px;
  margin: 0 auto;
  padding: 1rem;
}

.test-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 1.5rem;
  flex-wrap: wrap;
  gap: 0.75rem;
}

.test-header h2 {
  font-size: 1.5rem;
}

.btn-back {
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
  color: #667eea;
  text-decoration: none;
  font-size: 0.9rem;
}

.btn-back:hover {
  text-decoration: underline;
}

/* ======== Config Bar ======== */
.config-bar {
  display: flex;
  align-items: center;
  gap: 1rem;
  flex-wrap: wrap;
  margin-bottom: 1.5rem;
  padding: 1rem;
  background: #fff;
  border-radius: 12px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.06);
}

.config-bar label {
  font-size: 0.9rem;
  font-weight: 600;
}

.config-bar select,
.config-bar input[type="number"] {
  padding: 0.4rem 0.6rem;
  border: 2px solid #e0e0e0;
  border-radius: 8px;
  font-size: 0.9rem;
  outline: none;
  transition: border-color 0.2s;
}

.config-bar select:focus,
.config-bar input[type="number"]:focus {
  border-color: #667eea;
}

.config-bar input[type="number"] {
  width: 70px;
}

/* ======== Question ======== */
.question-list {
  list-style: none;
}

.question-item {
  background: #fff;
  border-radius: 12px;
  padding: 1rem 1.25rem;
  margin-bottom: 0.75rem;
  box-shadow: 0 2px 8px rgba(0,0,0,0.06);
  display: flex;
  align-items: center;
  gap: 0.75rem;
  flex-wrap: wrap;
}

.question-item .q-num {
  font-weight: 700;
  color: #667eea;
  min-width: 2rem;
}

.question-item .q-text {
  font-size: 1.1rem;
  font-weight: 600;
  min-width: 100px;
}

.question-item .q-input {
  padding: 0.4rem 0.6rem;
  border: 2px solid #e0e0e0;
  border-radius: 8px;
  font-size: 1rem;
  width: 100px;
  outline: none;
  transition: border-color 0.2s;
  text-align: center;
}

.question-item .q-input:focus {
  border-color: #667eea;
}

.question-item .q-result {
  font-size: 0.9rem;
  font-weight: 600;
  min-width: 60px;
}

.q-result.correct {
  color: #28a745;
}

.q-result.wrong {
  color: #dc3545;
}

/* ======== Buttons ======== */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.6rem 1.5rem;
  border: none;
  border-radius: 8px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.2s, transform 0.1s;
}

.btn:active {
  transform: scale(0.97);
}

.btn-primary {
  background: linear-gradient(135deg, #667eea, #764ba2);
  color: #fff;
}

.btn-primary:hover {
  opacity: 0.9;
}

.btn-success {
  background: #28a745;
  color: #fff;
}

.btn-success:hover {
  background: #218838;
}

.btn-outline {
  background: transparent;
  border: 2px solid #667eea;
  color: #667eea;
}

.btn-outline:hover {
  background: #667eea;
  color: #fff;
}

.btn-group {
  display: flex;
  gap: 0.75rem;
  flex-wrap: wrap;
  margin-top: 1rem;
}

/* ======== Result Panel ======== */
.result-panel {
  margin-top: 1.5rem;
  padding: 1.5rem;
  background: #fff;
  border-radius: 12px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.06);
  text-align: center;
}

.result-panel .score {
  font-size: 3rem;
  font-weight: 800;
  color: #667eea;
}

.result-panel .score-label {
  font-size: 1rem;
  color: #666;
}

.result-panel .detail {
  margin-top: 0.75rem;
  font-size: 0.9rem;
  color: #666;
}

/* ======== Timer ======== */
.timer {
  font-size: 1.1rem;
  font-weight: 700;
  color: #667eea;
}

/* ======== Responsive ======== */
@media (max-width: 600px) {
  .site-header h1 { font-size: 1.5rem; }
  .card-grid { grid-template-columns: 1fr; }
  .question-item { flex-direction: column; align-items: stretch; text-align: center; }
  .question-item .q-input { width: 100%; }
  .config-bar { flex-direction: column; align-items: stretch; }
}