/* Base resets */
* { box-sizing: border-box; }
html { -webkit-font-smoothing: antialiased; -moz-osx-font-smoothing: grayscale; }

/* Theme variables */
:root {
  --bg: #ffffff;
  --text: #1f2937;
  --text-strong: #111827;
  --muted: #6b7280;
  --muted-strong: #4b5563;
  --border: #e5e7eb;
  --link: #2563eb;
  --accent: #2563eb;
  --btn-bg: #ffffff;
  --btn-text: #111827;
  --btn-border: #d1d5db;
  --nav-bg: rgba(255, 255, 255, 0.8);
  --hover-bg: #f3f4f6;
  --card-bg: #ffffff;
  --tag-bg: #eef2ff;
  --tag-text: #3730a3;
}

/* System dark default via media query (no JS needed) */
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0b1220;            /* near slate-950 */
    --text: #e5e7eb;          /* slate-200 */
    --text-strong: #f9fafb;   /* slate-50 */
    --muted: #9ca3af;         /* slate-400 */
    --muted-strong: #cbd5e1;  /* slate-300 */
    --border: #2b3446;        /* dark border */
    --link: #93c5fd;          /* light blue */
    --accent: #3b82f6;        /* blue-500 */
    --btn-bg: #111827;        /* card dark */
    --btn-text: #e5e7eb;
    --btn-border: #334155;    /* slate-700 */
    --nav-bg: rgba(11, 18, 32, 0.85);
    --hover-bg: #1f2937;
    --card-bg: #111827;
    --tag-bg: #1f2937;
    --tag-text: #c7d2fe;
  }
}

/* Explicit overrides: user-chosen mode wins over system */
:root[data-theme="light"] {
  --bg: #ffffff;
  --text: #1f2937;
  --text-strong: #111827;
  --muted: #6b7280;
  --muted-strong: #4b5563;
  --border: #e5e7eb;
  --link: #2563eb;
  --accent: #2563eb;
  --btn-bg: #ffffff;
  --btn-text: #111827;
  --btn-border: #d1d5db;
  --nav-bg: rgba(255, 255, 255, 0.8);
  --hover-bg: #f3f4f6;
  --card-bg: #ffffff;
  --tag-bg: #eef2ff;
  --tag-text: #3730a3;
}
:root[data-theme="dark"] {
  --bg: #0b1220;
  --text: #e5e7eb;
  --text-strong: #f9fafb;
  --muted: #9ca3af;
  --muted-strong: #cbd5e1;
  --border: #2b3446;
  --link: #93c5fd;
  --accent: #3b82f6;
  --btn-bg: #111827;
  --btn-text: #e5e7eb;
  --btn-border: #334155;
  --nav-bg: rgba(11, 18, 32, 0.85);
  --hover-bg: #1f2937;
  --card-bg: #111827;
  --tag-bg: #1f2937;
  --tag-text: #c7d2fe;
}

body { margin: 0; font-family: system-ui, -apple-system, Segoe UI, Roboto, Ubuntu, Cantarell, Noto Sans, "Helvetica Neue", Arial, "Apple Color Emoji", "Segoe UI Emoji"; color: var(--text); background: var(--bg); }
img { max-width: 100%; display: block; }
a { color: var(--link); text-decoration: none; }
a:hover { text-decoration: underline; }

/* Layout */
.container { width: min(1100px, 92%); margin: 0 auto; }
header.site-header { position: sticky; top: 0; background: var(--nav-bg); backdrop-filter: saturate(180%) blur(8px); border-bottom: 1px solid var(--border); z-index: 50; }
.nav { display: flex; align-items: center; justify-content: space-between; padding: 0.9rem 0; }
.brand { display: flex; align-items: baseline; gap: .5rem; }
.brand a { font-weight: 700; color: var(--text-strong); font-size: 1.1rem; }
.brand small { color: var(--muted); }

.nav-links { display: flex; gap: 1rem; }
.nav-links a { padding: .4rem .7rem; border-radius: .45rem; color: var(--text-strong); }
.nav-links a.active, .nav-links a:hover { background: var(--hover-bg); text-decoration: none; }
.nav-links button { padding: .4rem .7rem; border-radius: .45rem; border: 1px solid var(--btn-border); background: var(--btn-bg); color: var(--btn-text); cursor: pointer; }
.nav-links button:hover { background: var(--hover-bg); }

/* Hero */
.hero { padding: 3rem 0 2rem; }
.hero h1 { font-size: clamp(1.8rem, 3.5vw + .5rem, 3rem); margin: 0 0 .5rem; line-height: 1.15; }
.hero p { color: var(--muted-strong); font-size: 1.05rem; max-width: 70ch; }
.hero .cta { margin-top: 1.25rem; display: flex; gap: .75rem; flex-wrap: wrap; }
.btn { display: inline-flex; align-items: center; gap: .5rem; padding: .6rem .9rem; border-radius: .55rem; border: 1px solid var(--btn-border); background: var(--btn-bg); color: var(--btn-text); font-weight: 600; }
.btn.primary { background: var(--accent); color: #fff; border-color: #1d4ed8; }
.btn:hover { filter: brightness(.98); text-decoration: none; }

/* Sections */
section { padding: 2rem 0; }
section h2 { font-size: 1.5rem; margin: 0 0 1rem; }
section p.lead { color: var(--muted-strong); max-width: 72ch; }

/* Cards & Grids */
.grid { display: grid; gap: 1rem; }
.grid.cards { grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); }
.card { padding: 1rem; border: 1px solid var(--border); border-radius: .75rem; background: var(--card-bg); }
.card h3 { margin: .25rem 0 .5rem; font-size: 1.1rem; }
.card p { color: var(--muted-strong); }
.card .meta { margin-top: .75rem; font-size: .9rem; color: var(--muted); }
.tag { display: inline-block; padding: .15rem .5rem; background: var(--tag-bg); color: var(--tag-text); border-radius: .4rem; font-size: .8rem; margin: .2rem .25rem .2rem 0; }

/* Footer */
footer { border-top: 1px solid var(--border); padding: 1.5rem 0; color: var(--muted); }

/* Utilities */
.muted { color: var(--muted); }
.stack-sm > * + * { margin-top: .4rem; }
.stack > * + * { margin-top: .8rem; }
.stack-lg > * + * { margin-top: 1.2rem; }
.center { text-align: center; }

/* Responsive nav (simple) */
@media (max-width: 640px) {
  .nav-links { gap: .4rem; }
  .nav-links a { padding: .35rem .55rem; }
}