/* ============================================================
   Concept: CSS Functions
   Built-in functions: var(), calc(), clamp(), min(), max(), rgb(), hsl(), url(), attr()...
   ============================================================ */

/* ---------- Base reset & typography ---------- */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}
body {
  font-family:
    system-ui,
    -apple-system,
    "Segoe UI",
    Roboto,
    sans-serif;
  line-height: 1.6;
  color: #1f2937;
  background: #f8fafc;
  padding: 2rem;
}
.page-header {
  max-width: 760px;
  margin: 0 auto 2rem;
}
.page-header h1 {
  font-size: 1.75rem;
  margin-bottom: 0.5rem;
  color: #0f172a;
}
.page-header .lead {
  color: #475569;
}
.demo {
  max-width: 760px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: 1rem;
}
.box {
  padding: 1rem;
  background: #fff;
  border: 1px solid #e2e8f0;
  border-radius: 8px;
}

:root {
  --pad: 1rem;
}
.fn {
  width: min(90%, 500px);
  padding: calc(var(--pad) * 2);
  font-size: clamp(1rem, 2vw, 1.4rem);
  color: rgb(15 23 42);
  background: hsl(210 100% 96%);
  background-image: url("https://picsum.photos/2/2");
  border: 2px solid oklch(0.7 0.15 250);
  border-radius: 12px;
}