:root {
  --primary: #2563eb;
  --primary-dark: #1d4ed8;
  --danger: #dc2626;
  --bg: #f8fafc;
  --card: #ffffff;
  --text: #1e293b;
  --text-light: #64748b;
  --border: #e2e8f0;
  --shadow: 0 1px 3px rgba(0,0,0,0.1);
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
}

/* Navbar */
.navbar {
  background: var(--card);
  border-bottom: 1px solid var(--border);
  padding: 0 1rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  position: sticky;
  top: 0;
  z-index: 100;
}

.nav-brand a {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--text);
  text-decoration: none;
}

.nav-links {
  display: flex;
  gap: 1rem;
}

.nav-links a {
  padding: 0.75rem 0.5rem;
  color: var(--text-light);
  text-decoration: none;
  font-size: 0.9rem;
  border-bottom: 2px solid transparent;
}

.nav-links a:hover, .nav-links a.active {
  color: var(--primary);
  border-bottom-color: var(--primary);
}

/* Container */
.container {
  max-width: 800px;
  margin: 0 auto;
  padding: 1rem;
  min-height: calc(100vh - 120px);
}

/* Hero */
.hero {
  text-align: center;
  padding: 2rem 0;
}

.hero h1 {
  font-size: 1.5rem;
  margin-bottom: 0.5rem;
}

.hero p {
  color: var(--text-light);
}

/* Posts Grid */
.posts-grid {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.post-card {
  background: var(--card);
  border-radius: 8px;
  border: 1px solid var(--border);
  overflow: hidden;
  cursor: pointer;
  transition: box-shadow 0.2s;
}

.post-card:hover {
  box-shadow: 0 4px 12px rgba(0,0,0,0.1);
}

.post-card-cover {
  width: 100%;
  height: 160px;
  object-fit: cover;
  background: var(--bg);
}

.post-card-body {
  padding: 1rem;
}

.post-card h3 {
  font-size: 1.1rem;
  margin-bottom: 0.5rem;
  line-height: 1.4;
}

.post-card-summary {
  color: var(--text-light);
  font-size: 0.9rem;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.post-card-meta {
  margin-top: 0.75rem;
  font-size: 0.8rem;
  color: var(--text-light);
}

/* Post Article */
.post-article {
  background: var(--card);
  border-radius: 8px;
  border: 1px solid var(--border);
  padding: 1.5rem;
}

.post-article h1 {
  font-size: 1.4rem;
  margin-bottom: 0.5rem;
}

.post-meta {
  color: var(--text-light);
  font-size: 0.85rem;
  margin-bottom: 1.5rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--border);
}

.post-cover {
  width: 100%;
  max-height: 300px;
  object-fit: cover;
  border-radius: 6px;
  margin-bottom: 1.5rem;
}

/* Markdown Content */
.markdown-body h1 { font-size: 1.5rem; margin: 1.5rem 0 0.75rem; }
.markdown-body h2 { font-size: 1.3rem; margin: 1.25rem 0 0.75rem; border-bottom: 1px solid var(--border); padding-bottom: 0.3rem; }
.markdown-body h3 { font-size: 1.1rem; margin: 1rem 0 0.5rem; }
.markdown-body p { margin: 0.75rem 0; }
.markdown-body ul, .markdown-body ol { margin: 0.75rem 0; padding-left: 1.5rem; }
.markdown-body li { margin: 0.25rem 0; }
.markdown-body blockquote { border-left: 4px solid var(--primary); padding-left: 1rem; color: var(--text-light); margin: 1rem 0; }
.markdown-body code { background: #f1f5f9; padding: 0.2rem 0.4rem; border-radius: 4px; font-size: 0.9em; }
.markdown-body pre { background: #1e293b; color: #e2e8f0; padding: 1rem; border-radius: 6px; overflow-x: auto; margin: 1rem 0; }
.markdown-body pre code { background: none; padding: 0; color: inherit; }
.markdown-body img { max-width: 100%; height: auto; border-radius: 4px; margin: 0.5rem 0; }
.markdown-body table { width: 100%; border-collapse: collapse; margin: 1rem 0; }
.markdown-body th, .markdown-body td { border: 1px solid var(--border); padding: 0.5rem; text-align: left; }
.markdown-body th { background: var(--bg); }
.markdown-body a { color: var(--primary); }

/* Pagination */
.pagination {
  display: flex;
  justify-content: center;
  gap: 0.5rem;
  margin: 2rem 0;
}

.pagination button {
  padding: 0.4rem 0.8rem;
  border: 1px solid var(--border);
  background: var(--card);
  border-radius: 4px;
  cursor: pointer;
}

.pagination button.active, .pagination button:hover {
  background: var(--primary);
  color: white;
  border-color: var(--primary);
}

/* Login */
.login-box {
  max-width: 360px;
  margin: 3rem auto;
  background: var(--card);
  padding: 2rem;
  border-radius: 8px;
  border: 1px solid var(--border);
}

.login-box h2 { margin-bottom: 1.5rem; text-align: center; }

.hint { text-align: center; color: var(--text-light); font-size: 0.85rem; margin-top: 1rem; }

/* Admin */
.admin-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1.5rem;
}

.admin-posts-list {
  background: var(--card);
  border-radius: 8px;
  border: 1px solid var(--border);
}

.admin-post-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1rem;
  border-bottom: 1px solid var(--border);
}

.admin-post-item:last-child { border-bottom: none; }

.admin-post-info h4 { font-size: 1rem; margin-bottom: 0.25rem; }
.admin-post-info span { font-size: 0.8rem; color: var(--text-light); }

.admin-post-actions {
  display: flex;
  gap: 0.5rem;
}

/* Modal */
.modal {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.5);
  z-index: 200;
  overflow-y: auto;
  padding: 1rem;
}

.modal-content {
  background: var(--card);
  max-width: 800px;
  margin: 2rem auto;
  border-radius: 8px;
  max-height: calc(100vh - 4rem);
  overflow-y: auto;
}

.modal-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1rem;
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  background: var(--card);
}

.btn-close {
  background: none;
  border: none;
  font-size: 1.5rem;
  cursor: pointer;
  color: var(--text-light);
}

/* Forms */
.post-form { padding: 1rem; }

.form-group {
  margin-bottom: 1rem;
}

.form-group label {
  display: block;
  margin-bottom: 0.4rem;
  font-weight: 500;
  font-size: 0.9rem;
}

.form-group input,
.form-group textarea {
  width: 100%;
  padding: 0.6rem;
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 0.95rem;
  font-family: inherit;
}

.form-group input:focus,
.form-group textarea:focus {
  outline: none;
  border-color: var(--primary);
}

.form-group textarea {
  resize: vertical;
  font-family: "SF Mono", Monaco, monospace;
  font-size: 0.9rem;
  line-height: 1.5;
}

.editor-toolbar {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin-bottom: 0.5rem;
  padding: 0.5rem;
  background: var(--bg);
  border-radius: 6px;
}

.editor-toolbar button {
  padding: 0.3rem 0.6rem;
  border: 1px solid var(--border);
  background: var(--card);
  border-radius: 4px;
  font-size: 0.8rem;
  cursor: pointer;
}

.editor-toolbar button:hover {
  background: var(--primary);
  color: white;
  border-color: var(--primary);
}

.btn-upload { color: var(--primary); }

.form-actions {
  display: flex;
  gap: 0.75rem;
  justify-content: flex-end;
  padding: 1rem;
  border-top: 1px solid var(--border);
}

.preview-area {
  padding: 1rem;
  border-top: 1px solid var(--border);
  background: var(--bg);
}

/* Cover Preview */
.cover-preview {
  margin: 0.5rem 0;
  border-radius: 6px;
  overflow: hidden;
  border: 1px solid var(--border);
  max-width: 300px;
}

.cover-preview img {
  width: 100%;
  max-height: 160px;
  object-fit: cover;
  display: block;
}

.cover-actions {
  display: flex;
  gap: 0.5rem;
  margin-top: 0.5rem;
}

/* Buttons */
.btn {
  padding: 0.5rem 1rem;
  border: 1px solid var(--border);
  background: var(--card);
  border-radius: 6px;
  cursor: pointer;
  font-size: 0.9rem;
}

.btn-primary {
  background: var(--primary);
  color: white;
  border-color: var(--primary);
}

.btn-primary:hover { background: var(--primary-dark); }

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

/* Loading */
.loading { text-align: center; padding: 2rem; color: var(--text-light); }

/* Empty */
.empty { text-align: center; padding: 3rem; color: var(--text-light); }

/* Footer */
.footer {
  text-align: center;
  padding: 1.5rem;
  color: var(--text-light);
  font-size: 0.85rem;
  border-top: 1px solid var(--border);
}

/* Katex */
.katex-display { margin: 1em 0; overflow-x: auto; }

/* Responsive */
@media (max-width: 600px) {
  .container { padding: 0.75rem; }
  .hero { padding: 1.5rem 0; }
  .hero h1 { font-size: 1.25rem; }
  .post-article { padding: 1rem; }
  .admin-post-item { flex-direction: column; align-items: flex-start; gap: 0.75rem; }
  .modal-content { margin: 0; max-height: 100vh; border-radius: 0; }
  .editor-toolbar button { font-size: 0.75rem; padding: 0.25rem 0.4rem; }
}