:root {
  --bg: #f4f7fb;
  --panel: #ffffff;
  --text: #182235;
  --muted: #68758a;
  --primary: #3264ff;
  --primary-dark: #214bd1;
  --line: #dfe6f2;
  --success: #18a058;
  --danger: #d03050;
  --shadow: 0 8px 24px rgba(31, 54, 92, 0.08);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  color: var(--text);
  background: var(--bg);
  font-family: "Microsoft YaHei", "PingFang SC", Arial, sans-serif;
}

a {
  color: inherit;
  text-decoration: none;
}

button,
input,
select,
textarea {
  font: inherit;
}

.site-header {
  padding: 16px min(5vw, 40px);
  background: linear-gradient(135deg, #15337a, #3264ff 58%, #7aa2ff);
  color: white;
}

.navbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  font-weight: 700;
  font-size: 18px;
}

.brand-mark {
  display: grid;
  width: 36px;
  height: 36px;
  place-items: center;
  border-radius: 10px;
  background: rgba(255, 255, 255, 0.2);
  box-shadow: inset 0 0 0 1px rgba(255, 255, 255, 0.28);
}

.nav-actions {
  display: flex;
  gap: 12px;
  align-items: center;
}

.container {
  width: min(1180px, calc(100% - 36px));
  margin: 24px auto 54px;
}

.layout {
  display: grid;
  grid-template-columns: 220px 1fr;
  gap: 20px;
}

.panel,
.card,
.form-card {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 16px;
  box-shadow: var(--shadow);
}

.sidebar {
  position: sticky;
  top: 18px;
  align-self: start;
  padding: 20px;
}

.sidebar h2,
.content-title h2,
.form-card h2 {
  margin: 0;
  font-size: 18px;
}

.category-list {
  display: grid;
  gap: 8px;
  margin-top: 16px;
}

.category-button {
  display: block;
  width: 100%;
  border: 0;
  border-radius: 12px;
  padding: 10px 12px;
  color: var(--text);
  background: #f5f8ff;
  text-align: left;
  cursor: pointer;
  transition: 0.2s ease;
}

.category-button:hover,
.category-button.active {
  color: white;
  background: var(--primary);
  transform: translateX(3px);
}

.content-title {
  display: flex;
  align-items: end;
  justify-content: space-between;
  gap: 18px;
  margin-bottom: 18px;
}

.content-title p {
  margin: 8px 0 0;
  color: var(--muted);
}

.tutorial-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 18px;
}

.card {
  overflow: hidden;
  cursor: pointer;
  transition: 0.2s ease;
}

.card:hover {
  transform: translateY(-2px);
  box-shadow: 0 12px 32px rgba(31, 54, 92, 0.12);
}

.card-image {
  width: 100%;
  height: 160px;
  object-fit: cover;
  display: block;
  background: linear-gradient(135deg, #d7e2ff, #f3f6ff);
}

.card-placeholder {
  display: grid;
  place-items: center;
  color: #3156bf;
  font-size: 36px;
  font-weight: 900;
}

.card-body {
  padding: 18px;
}

.card-body h3 {
  margin: 0 0 10px;
  font-size: 18px;
}

.card-body p {
  margin: 0;
  color: var(--muted);
  line-height: 1.7;
}

.tutorial-content {
  margin-top: 14px;
  padding-top: 14px;
  border-top: 1px solid var(--line);
  color: var(--text);
  line-height: 1.8;
}

.meta {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  margin-top: 14px;
  color: var(--muted);
  font-size: 13px;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border: 0;
  border-radius: 999px;
  padding: 9px 16px;
  color: white;
  background: var(--primary);
  cursor: pointer;
  font-weight: 600;
  transition: 0.2s ease;
}

.btn:hover {
  background: var(--primary-dark);
  transform: translateY(-1px);
}

.btn.light {
  color: white;
  background: rgba(255, 255, 255, 0.18);
  box-shadow: inset 0 0 0 1px rgba(255, 255, 255, 0.3);
}

.btn.secondary {
  color: var(--primary);
  background: #eef3ff;
}

.btn.danger {
  background: var(--danger);
}

.empty-state {
  padding: 40px;
  color: var(--muted);
  text-align: center;
}

.admin-container {
  width: min(1120px, calc(100% - 36px));
  margin: 24px auto 54px;
}

.admin-grid {
  display: grid;
  grid-template-columns: 1fr 0.9fr;
  gap: 20px;
  align-items: start;
}

.form-card {
  padding: 22px;
}

.form-grid {
  display: grid;
  gap: 14px;
  margin-top: 18px;
}

.field {
  display: grid;
  gap: 6px;
}

.field label {
  font-weight: 600;
  font-size: 14px;
}

.field input,
.field select,
.field textarea {
  width: 100%;
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 10px 12px;
  outline: none;
  background: #fbfdff;
}

.field textarea {
  min-height: 140px;
  resize: vertical;
  line-height: 1.7;
}

.field input:focus,
.field select:focus,
.field textarea:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(50, 100, 255, 0.1);
}

.notice {
  margin-top: 14px;
  padding: 11px 13px;
  border-radius: 12px;
  background: #eef8f1;
  color: var(--success);
  display: none;
}

.notice.error {
  background: #fff1f3;
  color: var(--danger);
}

.page-notice {
  display: block;
  margin: 0 0 18px;
}

.admin-list {
  display: grid;
  gap: 12px;
  margin-top: 18px;
}

.admin-item {
  display: grid;
  gap: 8px;
  padding: 14px;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: #fbfdff;
}

.admin-item h3 {
  margin: 0;
  font-size: 16px;
}

.admin-item p {
  margin: 0;
  color: var(--muted);
  line-height: 1.6;
  font-size: 14px;
}

.tutorial-detail {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 16px;
  box-shadow: var(--shadow);
  padding: 32px;
}

.detail-header {
  margin-bottom: 32px;
  padding-bottom: 24px;
  border-bottom: 2px solid var(--line);
}

.back-link {
  display: inline-block;
  margin-bottom: 16px;
  color: var(--primary);
  font-size: 14px;
  transition: 0.2s ease;
}

.back-link:hover {
  transform: translateX(-3px);
}

.detail-header h1 {
  margin: 0 0 12px;
  font-size: 32px;
  line-height: 1.3;
}

.detail-meta {
  display: flex;
  gap: 16px;
  color: var(--muted);
  font-size: 14px;
}

.detail-content {
  line-height: 1.9;
  font-size: 16px;
}

.detail-content img {
  max-width: 100%;
  height: auto;
  border-radius: 12px;
  margin: 16px 0;
}

.detail-content h1,
.detail-content h2,
.detail-content h3,
.detail-content h4,
.detail-content h5,
.detail-content h6 {
  margin: 24px 0 12px;
  line-height: 1.4;
}

.detail-content p {
  margin: 12px 0;
}

.detail-content ul,
.detail-content ol {
  margin: 12px 0;
  padding-left: 24px;
}

.detail-content li {
  margin: 8px 0;
}

.detail-content a {
  color: var(--primary);
  text-decoration: underline;
}

.detail-content code {
  padding: 2px 6px;
  background: #f5f8ff;
  border-radius: 4px;
  font-family: 'Consolas', 'Monaco', monospace;
  font-size: 0.9em;
}

.detail-content blockquote {
  margin: 16px 0;
  padding: 12px 20px;
  border-left: 4px solid var(--primary);
  background: #f5f8ff;
  color: var(--muted);
}

@media (max-width: 860px) {
  .layout,
  .admin-grid {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: static;
  }

  .navbar,
  .content-title {
    align-items: flex-start;
    flex-direction: column;
  }
}