:root {
  --color-bg: #f5f6f8;
  --color-surface: #ffffff;
  --color-text: #1f2430;
  --color-muted: #6b7280;
  --color-primary: #2563eb;
  --color-primary-dark: #1d4ed8;
  --color-secondary: #e5e7eb;
  --color-secondary-dark: #d1d5db;
  --color-success: #16a34a;
  --color-danger: #dc2626;
  --color-border: #e2e5ea;
  --radius: 8px;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Arial, sans-serif;
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.5;
}

.container {
  max-width: 960px;
  margin: 0 auto;
  padding: 0 16px;
}

a { color: var(--color-primary); text-decoration: none; }
a:hover { text-decoration: underline; }

.site-header {
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
}
.header-inner {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  padding: 12px 16px;
  gap: 8px;
}
.brand { font-weight: 700; font-size: 1.2rem; color: var(--color-text); }
.brand:hover { text-decoration: none; }
.main-nav a {
  margin-left: 16px;
  color: var(--color-muted);
  font-size: 0.95rem;
}
.main-nav a:first-child { margin-left: 0; }
.main-nav a:hover { color: var(--color-primary); text-decoration: none; }

main.container { padding-top: 24px; padding-bottom: 48px; }

.site-footer {
  text-align: center;
  color: var(--color-muted);
  font-size: 0.85rem;
  padding: 24px 0;
}

h1 { font-size: 1.6rem; margin: 0 0 16px; }
h2 { font-size: 1.25rem; margin: 32px 0 12px; }
h3 { font-size: 1.05rem; margin: 0 0 4px; }

.card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 20px;
  margin-bottom: 20px;
}

.notice-card { border-color: var(--color-primary); }

.flash {
  padding: 12px 16px;
  border-radius: var(--radius);
  margin-bottom: 16px;
  font-size: 0.95rem;
}
.flash-error { background: #fee2e2; color: #991b1b; }
.flash-success { background: #dcfce7; color: #14532d; }
.flash-info { background: #dbeafe; color: #1e3a8a; }

.btn {
  display: inline-block;
  padding: 10px 18px;
  border-radius: var(--radius);
  border: none;
  cursor: pointer;
  font-size: 0.95rem;
  font-weight: 600;
  text-align: center;
}
.btn:hover { text-decoration: none; }
.btn-primary { background: var(--color-primary); color: #fff; }
.btn-primary:hover { background: var(--color-primary-dark); }
.btn-secondary { background: var(--color-secondary); color: var(--color-text); }
.btn-secondary:hover { background: var(--color-secondary-dark); }
.btn-success { background: var(--color-success); color: #fff; }
.btn-danger { background: var(--color-danger); color: #fff; }
.btn-block { display: block; width: 100%; margin-top: 12px; }
.btn-sm { padding: 6px 12px; font-size: 0.85rem; }

.btn-row { display: flex; flex-wrap: wrap; gap: 10px; margin: 12px 0; }
.main-actions { margin: 20px 0; }

.stats-row { display: flex; flex-wrap: wrap; gap: 16px; margin-bottom: 16px; }
.stat-box {
  flex: 1 1 140px;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 16px;
  text-align: center;
}
.stat-value { font-size: 1.8rem; font-weight: 700; color: var(--color-primary); }
.stat-label { color: var(--color-muted); font-size: 0.85rem; margin-top: 4px; }

.topic-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 16px;
}
.topic-card { display: flex; flex-direction: column; }
.topic-meta { color: var(--color-muted); font-size: 0.9rem; margin: 2px 0; }

.empty-state { color: var(--color-muted); padding: 20px 0; }

form label {
  display: block;
  margin: 12px 0 4px;
  font-size: 0.9rem;
  font-weight: 600;
}
form input[type="text"],
form input[type="password"],
form input[type="file"],
form select,
form textarea {
  width: 100%;
  padding: 10px 12px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  font-size: 0.95rem;
  font-family: inherit;
  background: #fff;
  color: var(--color-text);
}
form textarea { resize: vertical; }
form button[type="submit"] { margin-top: 16px; }

.inline-filter { display: flex; align-items: center; gap: 10px; }
.inline-filter label { margin: 0; }
.inline-filter select { width: auto; }

.auth-page { display: flex; align-items: center; justify-content: center; min-height: 100vh; }
.auth-card { width: 100%; max-width: 360px; }
.auth-card h1 { text-align: center; }

.exam-progress { color: var(--color-muted); margin-bottom: 8px; }
.question-card { max-width: 640px; }
.question-text { font-size: 1.1rem; margin-bottom: 20px; white-space: pre-wrap; }

.options-list { display: flex; flex-direction: column; gap: 10px; margin-bottom: 16px; }
.option-item {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 12px 14px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  cursor: pointer;
}
.option-item:hover { border-color: var(--color-primary); }
.option-item input { margin: 0; }

.answer-text { font-size: 1.05rem; margin: 16px 0; }
.hidden { display: none; }

.tag {
  display: inline-block;
  padding: 2px 10px;
  border-radius: 999px;
  font-size: 0.85rem;
  font-weight: 600;
}
.tag-correct { background: #dcfce7; color: #14532d; }
.tag-wrong { background: #fee2e2; color: #991b1b; }

.meta-table { width: 100%; border-collapse: collapse; margin: 16px 0; }
.meta-table th, .meta-table td { text-align: left; padding: 6px 0; border-bottom: 1px solid var(--color-border); }
.meta-table th { width: 40%; color: var(--color-muted); font-weight: 600; }

.mistake-list, .wrong-list, .qa-list { display: flex; flex-direction: column; gap: 12px; }
.mistake-item p, .wrong-item p { margin: 6px 0; }

.qa-item { display: flex; flex-wrap: wrap; gap: 12px; justify-content: space-between; align-items: flex-start; }
.edit-question-form { flex: 1 1 320px; }

.table-wrap { overflow-x: auto; }
.data-table { width: 100%; border-collapse: collapse; background: var(--color-surface); }
.data-table th, .data-table td {
  padding: 10px 12px;
  border-bottom: 1px solid var(--color-border);
  text-align: left;
  font-size: 0.9rem;
  white-space: nowrap;
}
.data-table th { color: var(--color-muted); font-weight: 600; }

.inline-edit-form { display: flex; gap: 8px; align-items: center; }
.inline-edit-form input[type="text"] { width: auto; flex: 1; }

@media (max-width: 600px) {
  .header-inner { flex-direction: column; align-items: flex-start; }
  .main-nav a { margin-left: 0; margin-right: 14px; }
  .stats-row { flex-direction: column; }
}