/* --- CSS Variables & Themes --- */
:root {
  --bg: #ffffff;
  --text: #0f0f0f;
  --muted: #5a5a5a;
  --card: #f6f7f9;
  --border: #e7e7ea;
  --accent: #2f72ff;  /* blue-leaning for RG colorblind friendliness */
  --pill: #e9efff;
  --radius: 14px;
  --shadow: 0 6px 24px rgba(0,0,0,.06);
  --font-sans: ui-sans-serif, system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, "Apple Color Emoji", "Segoe UI Emoji";
}

html[data-theme="dark"] {
  --bg: #0b0d10;
  --text: #f2f4f8;
  --muted: #9aa4b2;
  --card: #131721;
  --border: #1e2633;
  --accent: #7aa2ff;
  --pill: #1b2a52;
  --shadow: 0 6px 24px rgba(0,0,0,.4);
}

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

body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-sans);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

/* --- Header --- */
.site-header {
  position: sticky; top: 0; z-index: 50;
  backdrop-filter: blur(8px);
  background: color-mix(in oklab, var(--bg) 80%, transparent);
  border-bottom: 1px solid var(--border);
  display: flex; align-items: center; justify-content: space-between;
  padding: 14px 18px;
}

.brand {
  font-weight: 800;
  letter-spacing: 0.2px;
  text-decoration: none;
  color: var(--text);
  font-size: 1.1rem;
}

.nav a {
  text-decoration: none;
  color: var(--text);
  opacity: 0.86;
  margin-right: 14px;
}
.nav a[aria-current="page"] { opacity: 1; }

.theme-toggle {
  border: 1px solid var(--border);
  background: var(--card);
  border-radius: 999px;
  padding: 6px 10px;
  cursor: pointer;
}

/* --- Layout --- */
.container {
  max-width: 1000px;
  margin: 0 auto;
  padding: 24px 18px 56px;
}

.hero { margin: 14px 0 12px; }
.hero h1 { margin: 8px 0 6px; font-size: 2rem; }
.sub { color: var(--muted); margin: 0 0 14px; }

/* --- Tag Filter --- */
.tag-filter { display: flex; flex-wrap: wrap; gap: 8px; }
.chip {
  border: 1px solid var(--border);
  background: var(--pill);
  color: var(--text);
  border-radius: 999px;
  font-size: 0.9rem;
  padding: 6px 12px;
  cursor: pointer;
  transition: transform .05s ease-in-out;
}
.chip:hover { transform: translateY(-1px); }
.chip.is-active {
  border-color: var(--accent);
  outline: 2px solid color-mix(in oklab, var(--accent) 35%, transparent);
}

/* --- Cards --- */
.grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(270px, 1fr));
  gap: 16px;
  margin-top: 12px;
}

.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  transition: transform .12s ease, border-color .12s ease;
}
.card:hover { transform: translateY(-2px); border-color: color-mix(in oklab, var(--accent) 25%, var(--border)); }

.card-link { display: block; text-decoration: none; color: inherit; padding: 18px; }

.card-title {
  margin: 0 0 6px;
  font-size: 1.15rem;
  line-height: 1.3;
}

.card-excerpt { margin: 0 0 10px; color: var(--muted); }

.meta { display: flex; align-items: center; gap: 10px; font-size: 0.9rem; color: var(--muted); }
.pill {
  display: inline-block;
  background: var(--pill);
  border: 1px solid var(--border);
  padding: 2px 8px;
  border-radius: 999px;
}

/* --- Footer --- */
.site-footer {
  border-top: 1px solid var(--border);
  color: var(--muted);
  font-size: 0.95rem;
  padding: 18px;
  text-align: center;
}

/* --- Basic a11y --- */
:focus-visible { outline: 3px solid var(--accent); outline-offset: 2px; }
img { max-width: 100%; height: auto; border-radius: 8px; }

/* --- Post layout & typography --- */
.post { max-width: 820px; margin: 0 auto; }
.post-header h1 { margin-top: 8px; margin-bottom: 6px; line-height: 1.2; }
.post .meta { color: var(--muted); margin-bottom: 18px; display: flex; gap: 10px; align-items: center; }

/* --- Breadcrumbs --- */
.breadcrumbs { font-size: 0.95rem; color: var(--muted); margin-bottom: 8px; }
.breadcrumbs a { color: inherit; text-decoration: none; border-bottom: 1px dashed var(--border); }

/* --- TOC --- */
.toc { border: 1px solid var(--border); background: var(--card); padding: 14px; border-radius: var(--radius); margin: 18px 0; }
.toc h2 { margin: 0 0 8px; font-size: 1.05rem; }
.toc ol { margin: 0; padding-left: 18px; }
.toc li { margin: 4px 0; }
.toc li.toc-sub { margin-left: 12px; list-style: circle; }

/* --- Tables --- */
.table-wrap { overflow-x: auto; }
table { width: 100%; border-collapse: collapse; margin: 10px 0 18px; }
thead th { text-align: left; border-bottom: 2px solid var(--border); padding: 8px; }
tbody td { border-bottom: 1px solid var(--border); padding: 8px; vertical-align: top; }

/* --- Figures --- */
figure { margin: 18px 0; }
figcaption { color: var(--muted); font-size: 0.95rem; margin-top: 6px; }