:root {
  color-scheme: light;
  --background: #edf5fb;
  --surface: #fff;
  --ink: #17232e;
  --muted: #435767;
  --accent: #165b83;
  --border: #c6d9e7;
}

* { box-sizing: border-box; }
html { scroll-padding-top: 1.5rem; }
body {
  margin: 0;
  background: var(--background);
  color: var(--ink);
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", "Hiragino Kaku Gothic ProN", "Yu Gothic", sans-serif;
  line-height: 1.85;
  overflow-wrap: anywhere;
}
a { color: var(--accent); text-underline-offset: .25em; }
a:hover { text-decoration-thickness: 2px; }
a:focus-visible { outline: 3px solid var(--accent); outline-offset: 5px; }
h1, h2, h3 { line-height: 1.5; }
h1 { margin: .7rem 0 1.5rem; font-size: clamp(2rem, 5vw, 3.4rem); }
h2 { margin: .5rem 0 1rem; font-size: clamp(1.4rem, 3vw, 2rem); }
h3 { font-size: 1.15rem; }
p { margin: .75rem 0; }
.container { width: min(100% - 2.5rem, 1060px); margin-inline: auto; }
.skip-link { position: absolute; left: 1rem; top: -10rem; padding: .6rem 1rem; background: white; }
.skip-link:focus { top: 1rem; }
.site-header { background: var(--surface); border-bottom: 1px solid var(--border); }
.header-inner { display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: .5rem 2rem; padding-block: 1.2rem; }
.site-name { color: var(--ink); font-weight: 700; text-decoration: none; }
nav { display: flex; flex-wrap: wrap; gap: .2rem 1.2rem; }
nav a { display: inline-block; padding-block: .5rem; font-size: .9rem; }
.hero { padding-block: clamp(3rem, 8vw, 6rem) 3rem; }
.eyebrow { margin: 0; color: var(--accent); font-size: .8rem; font-weight: 700; letter-spacing: .13em; }
.lead { font-size: 1.1rem; }
.notice { max-width: 48rem; padding: 1rem 1.2rem; border-left: 3px solid var(--accent); background: #dfedf7; }
.overview { margin-bottom: 3rem; }
.section-heading { margin-bottom: 1.75rem; }
.forum-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 1.5rem; }
.summary-card { background: var(--surface); padding: 2rem; border: 1px solid var(--border); border-radius: .75rem; }
.summary-card h3 { margin: .6rem 0; font-size: 1.35rem; }
.summary-card p:not(.eyebrow) { color: var(--muted); }
.button { display: inline-block; margin-top: 1rem; padding: .65rem 1.2rem; border: 1px solid var(--accent); border-radius: .3rem; text-decoration: none; font-weight: 600; }
.button:hover { background: #e5f1fa; }
.forum-detail { margin-block: 2rem; padding: clamp(1.25rem, 4vw, 3rem); border: 1px solid var(--border); border-radius: .75rem; background: var(--surface); }
.forum-detail section + section { margin-top: 2rem; }
.event-facts { margin: 0; }
.event-facts div { display: grid; grid-template-columns: 10rem minmax(0, 1fr); gap: 1rem; padding-block: .85rem; border-bottom: 1px solid var(--border); }
dt { font-weight: 600; }
dd { margin: 0; }
.placeholder { color: var(--muted); padding-block: .75rem; }
.registration { padding: 1.3rem; background: var(--background); border-radius: .5rem; }
.registration h3 { margin-top: 0; }
.status { display: inline-block; padding: .35rem .9rem; border: 1px solid var(--border); border-radius: .3rem; color: var(--muted); font-size: .9rem; }
.archive-guide { margin-block: 3rem; padding-block: 1rem; }
.site-footer { border-top: 1px solid var(--border); padding-block: 2rem; font-size: .9rem; }
.archive-page { padding-block: 3rem 5rem; min-height: 65vh; }
.archive-empty { padding: 1.5rem; background: var(--surface); border: 1px solid var(--border); border-radius: .5rem; }

@media (max-width: 640px) {
  .container { width: calc(100% - 2rem); }
  .forum-grid { grid-template-columns: 1fr; }
  .summary-card { padding: 1.5rem; }
  .event-facts div { grid-template-columns: 1fr; gap: .2rem; }
}