:root {
  color: #1c2721;
  background: #f6f5ef;
  font: 16px/1.65 system-ui, sans-serif;
  --accent: #215640;
  --muted: #4f6056;
  --border: #ced6cd;
}
* { box-sizing: border-box; }
body, h1, h2, p, dl, dd { margin: 0; }
a { color: var(--accent); }
a:focus-visible, summary:focus-visible { outline: 3px solid #356cb0; outline-offset: 3px; }
.shell { width: min(100% - 2.5rem, 44rem); margin-inline: auto; }
.site-header { border-bottom: 1px solid var(--border); padding-block: .5rem; font-weight: 700; }
.site-header .shell { display: flex; align-items: center; min-height: 44px; }
.site-header a { color: inherit; text-decoration: none; display: inline-flex; align-items: center; min-height: 44px; }
main { padding-block: 1rem 3rem; }
.index { padding-top: 2rem; }
.course-list { display: grid; gap: .65rem; }
.example-list { margin: 1rem 0 0; padding: 0; list-style: none; }
.example-list li + li { margin-top: .75rem; }
.lesson-nav { display: flex; flex-wrap: wrap; gap: .5rem 1rem; margin-top: 1.5rem; }
.speed { display: inline-flex; align-items: center; gap: .5rem; }
select { min-height: 44px; padding-inline: .5rem; font: inherit; }
.recordings { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: .6rem 1rem; }
.recording { display: grid; gap: .25rem; color: var(--muted); }
.recording audio { width: 100%; }
h1 { font-size: clamp(1.85rem, 5vw, 2.8rem); line-height: 1.18; text-wrap: balance; }
h2 { font-size: 1.3rem; line-height: 1.35; margin-bottom: .55rem; }
p { margin-top: .65rem; }
.intro { max-width: 31rem; margin-block: 1rem 2.25rem; }
.meta, dt { font-size: .875rem; color: var(--muted); }
.lesson-link { display: grid; gap: .3rem; padding: .8rem 1rem; border: 1px solid var(--border); border-radius: .55rem; background: #fffefa; text-decoration: none; }
.lesson-link strong { font-size: 1.2rem; text-decoration: underline; text-underline-offset: .2em; }
.lesson-link span:last-child { color: var(--muted); }
.back { display: inline-flex; align-items: center; min-height: 44px; }
.lesson-intro { margin-block: .75rem 1.9rem; padding: 1.3rem; color: #fffefa; background: #204637; border-radius: .75rem; }
.lesson-intro .meta { color: #d8e7df; margin: 0 0 .35rem; }
.lesson-intro p:last-child { margin: .75rem 0 0; }
section + section { margin-top: 2.25rem; }
details { border-top: 1px solid var(--border); }
details:first-of-type { margin-top: .85rem; }
details:last-of-type { border-bottom: 1px solid var(--border); }
summary { min-height: 44px; padding: .6rem 0; font-weight: 650; cursor: pointer; }
details > p { margin-inline: .85rem; }
.pair { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 1rem; padding: .75rem .85rem 1rem; }
dt { font-weight: 700; margin-bottom: .25rem; }
dd { overflow-wrap: anywhere; }
[lang="ja"] { font-family: "Yu Gothic", "Meiryo", "Hiragino Sans", sans-serif; }
footer { margin-top: 1.5rem; }
@media (max-width: 39rem) {
  .pair { grid-template-columns: 1fr; gap: .75rem; }
  .recordings { grid-template-columns: 1fr; }
}