:root {
  color-scheme: light;
  --ink: #17212b;
  --muted: #5e6b78;
  --line: #d7dfe6;
  --paper: #f7f9fb;
  --card: #ffffff;
  --accent: #146c94;
  --accent-dark: #0e4d6a;
  --warm: #e9a23b;
  --danger: #9f2d31;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

* { box-sizing: border-box; }
body { margin: 0; color: var(--ink); background: var(--paper); line-height: 1.5; }
a { color: var(--accent-dark); }
.site-header, main, footer { width: min(1120px, calc(100% - 40px)); margin: 0 auto; }
.site-header { display: flex; justify-content: space-between; align-items: center; padding: 24px 0; }
.brand { color: var(--ink); display: inline-flex; gap: 10px; align-items: center; font-size: 1.15rem; font-weight: 800; text-decoration: none; }
.brand-mark { color: var(--accent); font-size: 2rem; line-height: .7; }
.repo-link { font-size: .9rem; text-decoration: none; }
.hero { display: grid; grid-template-columns: 1.25fr .75fr; align-items: center; gap: 48px; padding: 72px 0 64px; }
.eyebrow, .step-label { color: var(--accent-dark); font-size: .76rem; font-weight: 800; letter-spacing: .12em; text-transform: uppercase; }
.hero h1 { max-width: 700px; margin: 12px 0 18px; font-size: clamp(2.4rem, 6vw, 4.8rem); letter-spacing: -.055em; line-height: .98; }
.lede { max-width: 680px; color: var(--muted); font-size: 1.12rem; }
.network-visual { display: grid; gap: 12px; justify-items: center; padding: 36px 18px; border: 1px solid var(--line); border-radius: 22px; background: #e8f3f7; color: var(--accent-dark); font: 700 clamp(1rem, 2vw, 1.35rem)/1.2 ui-monospace, SFMono-Regular, Menlo, monospace; transform: rotate(2deg); }
.network-visual strong { color: var(--warm); font-size: 2rem; }
.checker, .results { margin: 12px 0 56px; padding: 34px; border: 1px solid var(--line); border-radius: 18px; background: var(--card); box-shadow: 0 12px 30px rgb(23 33 43 / 5%); }
.section-heading { display: flex; justify-content: space-between; gap: 20px; align-items: start; margin-bottom: 22px; }
.section-heading h2, .boundary h2 { margin: 4px 0 0; font-size: clamp(1.45rem, 3vw, 2.1rem); letter-spacing: -.03em; }
.step-label { margin: 0; }
.text-button, .secondary-button { border: 0; background: transparent; color: var(--accent-dark); cursor: pointer; font: inherit; font-weight: 700; padding: 8px 0; }
label { display: grid; gap: 8px; font-weight: 700; }
textarea, input { width: 100%; border: 1px solid #b9c6d1; border-radius: 10px; color: var(--ink); background: #fff; font: 500 1rem/1.5 ui-monospace, SFMono-Regular, Menlo, monospace; padding: 12px 14px; }
textarea { resize: vertical; }
textarea:focus, input:focus, button:focus-visible { outline: 3px solid rgb(20 108 148 / 25%); outline-offset: 2px; border-color: var(--accent); }
.field-note, .summary { color: var(--muted); font-size: .9rem; }
.option-row { display: flex; align-items: end; gap: 16px; margin-top: 22px; }
.option-row label { flex: 0 1 210px; font-size: .88rem; }
.primary-button { border: 0; border-radius: 9px; background: var(--accent); color: white; cursor: pointer; font: inherit; font-weight: 800; padding: 12px 18px; }
.primary-button:hover { background: var(--accent-dark); }
.error { margin-top: 18px; padding: 14px 16px; border-left: 4px solid var(--danger); border-radius: 6px; background: #fff1f1; color: var(--danger); white-space: pre-line; }
.results h3 { margin-top: 34px; }
.table-wrap { overflow-x: auto; }
table { width: 100%; border-collapse: collapse; font-size: .91rem; }
th, td { border-bottom: 1px solid var(--line); padding: 12px 10px; text-align: left; vertical-align: top; }
thead th { color: var(--muted); font-size: .75rem; letter-spacing: .08em; text-transform: uppercase; }
tbody th, td:nth-child(3), td:nth-child(4), td:nth-child(5) { font-family: ui-monospace, SFMono-Regular, Menlo, monospace; }
details { margin-top: 28px; }
summary { cursor: pointer; font-weight: 800; }
pre { overflow-x: auto; padding: 18px; border-radius: 10px; background: #15212b; color: #e6f4f7; font: .82rem/1.6 ui-monospace, SFMono-Regular, Menlo, monospace; }
.boundary { padding: 22px 0 76px; }
.boundary-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 30px; color: var(--muted); }
footer { display: flex; justify-content: space-between; gap: 20px; padding: 26px 0 40px; color: var(--muted); font-size: .86rem; }
.sr-only { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0, 0, 0, 0); white-space: nowrap; }
@media (max-width: 720px) {
  .site-header, main, footer { width: min(100% - 28px, 1120px); }
  .hero { grid-template-columns: 1fr; gap: 24px; padding: 48px 0; }
  .network-visual { transform: none; }
  .checker, .results { padding: 22px 18px; }
  .option-row, .boundary-grid, footer { display: grid; grid-template-columns: 1fr; }
  .option-row label { max-width: none; }
  .repo-link { font-size: .78rem; }
}