:root {
  --bg: #eef1f7;
  --bg-2: #e3e9f5;
  --bg-soft: #f5f6f8;
  --surface: #ffffff;
  --border: #e2e5ea;
  --text: #1c2024;
  --text-muted: #5c6670;
  --accent: #2f6fed;
  --accent-hover: #1e59d4;
  --code-bg: #f5f6f8;
  --shadow: 0 1px 3px rgba(0,0,0,.06), 0 1px 2px rgba(0,0,0,.04);
  --radius: 14px;
  --maxw: 1180px;
  --readw: 760px;

  /* Glass */
  --glass-bg: rgba(255, 255, 255, 0.55);
  --glass-bg-strong: rgba(255, 255, 255, 0.72);
  --glass-border: rgba(255, 255, 255, 0.7);
  --glass-shadow: 0 8px 30px rgba(23, 43, 92, 0.10);
  --glass-blur: 16px;
  --mesh-1: rgba(47, 111, 237, 0.20);
  --mesh-2: rgba(120, 90, 240, 0.16);
  --mesh-3: rgba(35, 190, 190, 0.14);
}

[data-theme="dark"] {
  --bg: #0f1216;
  --bg-2: #141a24;
  --bg-soft: #1b1f26;
  --surface: #1b1f26;
  --border: #2a2f38;
  --text: #e6e9ee;
  --text-muted: #97a1ad;
  --accent: #5b8dff;
  --accent-hover: #7aa2ff;
  --code-bg: #0f1216;
  --shadow: none;

  --glass-bg: rgba(27, 31, 38, 0.55);
  --glass-bg-strong: rgba(27, 31, 38, 0.75);
  --glass-border: rgba(255, 255, 255, 0.08);
  --glass-shadow: 0 8px 30px rgba(0, 0, 0, 0.35);
  --glass-blur: 18px;
  --mesh-1: rgba(47, 111, 237, 0.22);
  --mesh-2: rgba(120, 90, 240, 0.20);
  --mesh-3: rgba(35, 190, 190, 0.16);
}

* { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  font-size: 18px;
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  min-height: 100vh;
}

/* Vector background mesh (behind everything) */
.bg-mesh {
  position: fixed;
  inset: 0;
  z-index: -1;
  background:
    radial-gradient(38% 42% at 12% 8%, var(--mesh-1) 0%, transparent 60%),
    radial-gradient(34% 40% at 88% 14%, var(--mesh-2) 0%, transparent 60%),
    radial-gradient(46% 46% at 70% 92%, var(--mesh-3) 0%, transparent 62%),
    linear-gradient(160deg, var(--bg) 0%, var(--bg-2) 100%);
}

.container { width: 100%; max-width: var(--maxw); margin: 0 auto; padding: 0 20px; }

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

/* Glass surface utility */
.glass {
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius);
  box-shadow: var(--glass-shadow);
  -webkit-backdrop-filter: blur(var(--glass-blur)) saturate(160%);
  backdrop-filter: blur(var(--glass-blur)) saturate(160%);
}

/* Header */
.site-header {
  position: sticky; top: 0; z-index: 50;
  background: var(--glass-bg-strong);
  border-bottom: 1px solid var(--glass-border);
  -webkit-backdrop-filter: blur(var(--glass-blur)) saturate(160%);
  backdrop-filter: blur(var(--glass-blur)) saturate(160%);
}
.header-inner {
  display: flex; align-items: center; gap: 18px;
  padding-top: 12px; padding-bottom: 12px;
  flex-wrap: wrap;
}
.logo { display: inline-flex; align-items: center; gap: 10px; font-weight: 700; font-size: 1.25rem; color: var(--text); }
.logo:hover { text-decoration: none; }
.logo-mark { flex: none; display: block; }
.logo-mark-box { fill: var(--accent); opacity: .16; stroke: var(--accent); stroke-width: 1.4; }
.logo-mark-glyph { stroke: var(--accent); }
.logo-word { letter-spacing: -.01em; }

.main-nav { display: flex; gap: 6px; flex: 1; flex-wrap: wrap; }
.main-nav a {
  color: var(--text-muted); font-size: .95rem;
  padding: 6px 14px; border-radius: 999px; border: 1px solid transparent;
  transition: background .15s, color .15s, border-color .15s;
}
.main-nav a:hover { text-decoration: none; color: var(--text); background: var(--glass-bg); }
.main-nav a.is-active {
  color: var(--accent); border-color: var(--glass-border);
  background: var(--glass-bg);
}

.search-form input {
  padding: 8px 14px; border: 1px solid var(--glass-border); border-radius: 999px;
  background: var(--glass-bg); color: var(--text); font-size: .9rem; width: 160px;
  -webkit-backdrop-filter: blur(8px); backdrop-filter: blur(8px);
}
.theme-toggle {
  border: 1px solid var(--glass-border); background: var(--glass-bg); color: var(--text);
  width: 40px; height: 40px; border-radius: 50%; cursor: pointer; font-size: 1.1rem;
  -webkit-backdrop-filter: blur(8px); backdrop-filter: blur(8px);
  transition: background .15s;
}
.theme-toggle:hover { background: var(--glass-bg-strong); }
[data-theme="dark"] .theme-icon-dark { display: none; }
[data-theme="light"] .theme-icon-light,
:root:not([data-theme="dark"]) .theme-icon-light { display: none; }

/* Layout: 3/4 content + 1/4 sidebar */
.main-content { padding: 36px 20px 60px; }
.layout-with-sidebar {
  display: grid;
  grid-template-columns: 3fr 1fr;
  gap: 34px;
  align-items: start;
}
.layout-full { max-width: var(--readw); }
.sidebar { position: sticky; top: 84px; display: flex; flex-direction: column; gap: 18px; }

.page-title { font-size: 2rem; margin: 0 0 8px; letter-spacing: -.02em; }
.page-lead { color: var(--text-muted); margin-top: 0; }
.empty { color: var(--text-muted); }

/* Sidebar cards */
.sidebar-card { padding: 16px 18px; }
.sidebar-title { margin: 0 0 10px; font-size: .95rem; letter-spacing: .02em; text-transform: uppercase; color: var(--text-muted); }
.sidebar-list { list-style: none; margin: 0; padding: 0; display: flex; flex-direction: column; gap: 8px; }
.sidebar-list a { color: var(--text); font-size: .95rem; }
.sidebar-list a:hover { color: var(--accent); text-decoration: none; }
.sidebar-list .muted { color: var(--text-muted); font-size: .9rem; }

/* Post cards */
.post-grid { display: grid; gap: 24px; }
.post-card {
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius); overflow: hidden;
  box-shadow: var(--glass-shadow);
  -webkit-backdrop-filter: blur(var(--glass-blur)) saturate(160%);
  backdrop-filter: blur(var(--glass-blur)) saturate(160%);
  transition: transform .18s ease, box-shadow .18s ease;
}
.post-card:hover { transform: translateY(-3px); box-shadow: 0 14px 40px rgba(23, 43, 92, 0.16); }
.post-card-cover img { width: 100%; height: 220px; object-fit: cover; display: block; }
.post-card-body { padding: 20px 22px 24px; }
.post-card-title { font-size: 1.5rem; margin: 6px 0 10px; letter-spacing: -.015em; }
.post-card-title a { color: var(--text); }
.post-card-excerpt { color: var(--text-muted); margin: 0 0 14px; }
.post-meta { display: flex; gap: 10px; align-items: center; flex-wrap: wrap; color: var(--text-muted); font-size: .85rem; }
.pill {
  background: var(--glass-bg-strong); border: 1px solid var(--glass-border);
  padding: 2px 10px; border-radius: 999px; font-size: .8rem; color: var(--text-muted);
}
.pill-section { font-weight: 600; }
.pill-article { color: var(--accent); border-color: color-mix(in srgb, var(--accent) 40%, transparent); }
.pill-news { color: #b26b00; border-color: rgba(178,107,0,.35); }
[data-theme="dark"] .pill-news { color: #f0b45a; border-color: rgba(240,180,90,.3); }
.tag-list { display: flex; flex-wrap: wrap; gap: 8px; }
.tag { color: var(--text-muted); font-size: .85rem; }
.tag:hover { color: var(--accent); text-decoration: none; }

/* Placeholder (courses) */
.placeholder-card { text-align: center; padding: 60px 30px; }
.placeholder-icon { color: var(--accent); opacity: .8; margin-bottom: 8px; }
.placeholder-card .btn { margin-top: 18px; }

/* Full post */
.post-full-title { font-size: 2.4rem; line-height: 1.2; margin: 10px 0 0; letter-spacing: -.02em; }
.post-full-cover { width: 100%; border-radius: var(--radius); margin: 24px 0; }
.post-full-tags { margin: 30px 0; }
.views { margin-left: auto; }

.post-content { font-size: 1.075rem; }
.post-content h2 { font-size: 1.7rem; margin-top: 2em; letter-spacing: -.01em; }
.post-content h3 { font-size: 1.35rem; margin-top: 1.6em; }
.post-content img { max-width: 100%; border-radius: 8px; }
.post-content video { max-width: 100%; border-radius: 8px; }
.post-content blockquote {
  border-left: 3px solid var(--accent); margin: 1.4em 0; padding: .2em 1.2em;
  color: var(--text-muted); background: var(--glass-bg); border-radius: 0 8px 8px 0;
}
.post-content table { border-collapse: collapse; width: 100%; margin: 1.4em 0; font-size: .95rem; }
.post-content th, .post-content td { border: 1px solid var(--border); padding: 8px 12px; text-align: left; }
.post-content th { background: var(--bg-soft); }

.post-content code {
  font-family: "SF Mono", "JetBrains Mono", "Fira Code", ui-monospace, Menlo, Consolas, monospace;
  font-size: .9em; background: var(--code-bg); padding: .15em .4em; border-radius: 5px;
}
.post-content pre {
  background: var(--code-bg); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 16px 18px; overflow-x: auto; line-height: 1.5;
}
.post-content pre code { background: none; padding: 0; font-size: .9rem; }
.codehilite { background: var(--code-bg); border-radius: var(--radius); }

/* Comments */
.comments { margin-top: 50px; border-top: 1px solid var(--border); padding-top: 30px; }
.comment {
  border: 1px solid var(--glass-border); border-radius: var(--radius);
  padding: 14px 18px; margin-bottom: 14px; background: var(--glass-bg);
  -webkit-backdrop-filter: blur(10px); backdrop-filter: blur(10px);
}
.comment-head { display: flex; justify-content: space-between; color: var(--text-muted); font-size: .85rem; margin-bottom: 6px; }
.comment-body { color: var(--text); }
.comment-form { display: flex; flex-direction: column; gap: 12px; margin-top: 16px; }
.form-row { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }
.comment-form input, .comment-form textarea {
  width: 100%; padding: 10px 12px; border: 1px solid var(--glass-border);
  border-radius: 8px; background: var(--glass-bg); color: var(--text); font: inherit; font-size: .95rem;
}
.btn {
  display: inline-block; background: var(--accent); color: #fff; border: none;
  padding: 10px 20px; border-radius: 8px; font: inherit; font-weight: 600; cursor: pointer; align-self: flex-start;
}
.btn:hover { background: var(--accent-hover); color: #fff; text-decoration: none; }
.form-note, .form-error { color: var(--text-muted); font-size: .85rem; margin: 0; }
.form-error { color: #d94b4b; }

/* Pagination */
.pagination { display: flex; gap: 18px; align-items: center; justify-content: center; margin-top: 40px; }
.pagination-info { color: var(--text-muted); font-size: .9rem; }

.notice { text-align: center; padding: 40px 0; }

/* Footer */
.site-footer { border-top: 1px solid var(--glass-border); padding: 30px 0; color: var(--text-muted); font-size: .9rem; }

@media (max-width: 900px) {
  .layout-with-sidebar { grid-template-columns: 1fr; }
  .sidebar { position: static; flex-direction: row; flex-wrap: wrap; }
  .sidebar-card { flex: 1 1 220px; }
}

@media (max-width: 640px) {
  body { font-size: 17px; }
  .main-nav { order: 3; width: 100%; }
  .form-row { grid-template-columns: 1fr; }
  .post-full-title { font-size: 1.8rem; }
  .search-form input { width: 120px; }
  .logo-word { display: none; }
}