:root {
  color-scheme: light dark;
  --paper: #f7f7f5;
  --ink: #1c1c1c;
  --muted: #686862;
  --line: #d9d9d5;
  --dark: #1c1c1c;
  --light: #f7f7f5;
  font-family: ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", "Hiragino Sans", "Noto Sans JP", sans-serif;
}

* { box-sizing: border-box; }
html { background: var(--paper); color: var(--ink); }
body { margin: 0; min-width: 320px; }
a { color: inherit; }
main { width: min(1120px, calc(100% - 32px)); margin: 0 auto; padding: 48px 0 72px; }
header { display: grid; gap: 10px; padding-bottom: 24px; border-bottom: 1px solid var(--line); }
h1, h2, p { margin: 0; }
h1 { font-size: clamp(2rem, 6vw, 4rem); line-height: .95; letter-spacing: -.055em; }
.eyebrow, .meta { color: var(--muted); font-size: .82rem; font-weight: 700; letter-spacing: .06em; text-transform: uppercase; }
.lead { max-width: 58ch; color: var(--muted); line-height: 1.65; }
.back { width: fit-content; color: var(--muted); font-size: .9rem; }
.group-list, .concept-grid { list-style: none; padding: 0; margin: 28px 0 0; display: grid; gap: 1px; background: var(--line); border: 1px solid var(--line); }
.group-list { grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); }
.group-card, .concept-card { background: var(--paper); }
.group-card a { display: grid; gap: 8px; min-height: 160px; padding: 24px; text-decoration: none; }
.group-card a:hover h2 { text-decoration: underline; text-underline-offset: .15em; }
.group-card h2 { font-size: 1.5rem; }
.concept-grid { grid-template-columns: repeat(auto-fit, minmax(310px, 1fr)); }
.concept-card { min-width: 0; }
.concept-copy { display: grid; gap: 6px; padding: 18px 18px 16px; }
.concept-copy h2 { font-size: 1rem; }
.concept-copy p { color: var(--muted); font-size: .9rem; line-height: 1.5; }
.previews { display: grid; grid-template-columns: 1fr 1fr; border-top: 1px solid var(--line); }
.preview { min-height: 190px; padding: 18px; display: grid; align-content: center; justify-items: center; gap: 16px; color-scheme: only light; }
.preview.light { background: var(--light); color: var(--dark); }
.preview.dark { background: var(--dark); color: var(--light); }
.sizes { width: 100%; display: flex; align-items: end; justify-content: space-around; gap: 10px; }
.size { display: grid; justify-items: center; gap: 8px; font-size: .7rem; }
.size > span { opacity: .72; }
.size img { display: block; width: var(--size); height: var(--size); }
.preview.dark img { filter: invert(1); }
.file-link { display: block; padding: 12px 18px; border-top: 1px solid var(--line); color: var(--muted); font: .78rem/1.4 ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; text-decoration: none; overflow-wrap: anywhere; }
.empty { margin-top: 28px; padding: 32px; border: 1px solid var(--line); color: var(--muted); line-height: 1.7; }
footer { margin-top: 32px; color: var(--muted); font-size: .8rem; }

@media (prefers-color-scheme: dark) {
  :root { --paper: #191919; --ink: #f3f3ef; --muted: #aaa9a1; --line: #3c3c38; }
}

@media (max-width: 640px) {
  main { width: min(100% - 24px, 1120px); padding-top: 28px; }
  .previews { grid-template-columns: 1fr; }
}