:root {
  color-scheme: light;
  --bg: #f7f8fa;
  --panel: #fff;
  --ink: #1b2430;
  --muted: #667085;
  --line: #e3e7ee;
  --accent: #2b4a6f;
  --accent-soft: #eef3f9;
  --warn: #b3261e;
  padding-top: env(safe-area-inset-top, 0px);
  padding-bottom: env(safe-area-inset-bottom, 0px);
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #12161c;
    --panel: #1b2029;
    --ink: #e8ecf2;
    --muted: #9aa5b5;
    --line: #2b323d;
    --accent: #8fb6e0;
    --accent-soft: #212a36;
    --warn: #ef8079;
  }
}
:root[data-theme="dark"] {
  --bg: #12161c;
  --panel: #1b2029;
  --ink: #e8ecf2;
  --muted: #9aa5b5;
  --line: #2b323d;
  --accent: #8fb6e0;
  --accent-soft: #212a36;
  --warn: #ef8079;
}

* { box-sizing: border-box; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font: 15px/1.85 -apple-system, BlinkMacSystemFont, "Hiragino Sans", "Noto Sans JP", sans-serif;
}
img { max-width: 100%; }
[hidden] { display: none !important; }

.bar {
  position: sticky;
  top: env(safe-area-inset-top, 0px);
  z-index: 10;
  display: flex;
  align-items: center;
  min-height: 52px;
  padding: 0 16px;
  background: var(--panel);
  border-bottom: 1px solid var(--line);
}
.brand { font-weight: 700; letter-spacing: .02em; }
.back { color: var(--accent); text-decoration: none; font-weight: 600; }
.back:hover { text-decoration: underline; }

main { max-width: 760px; margin: 0 auto; padding: 24px 16px 64px; }

.hero { margin: 8px 0 28px; }
.hero h1 { margin: 0 0 6px; font-size: 26px; letter-spacing: .01em; }
.hero p { margin: 0; color: var(--muted); }

.block { margin: 0 0 32px; }
.blockhead {
  display: flex; align-items: baseline; gap: 10px; flex-wrap: wrap;
  margin: 0 0 12px; font-size: 15px; letter-spacing: .04em; color: var(--muted);
  text-transform: none;
}
.blockhead small { font-weight: 400; color: var(--muted); opacity: .8; }

/* course cards */
.cards { display: grid; gap: 12px; }
.card {
  display: flex; align-items: center; gap: 14px;
  padding: 18px; background: var(--panel);
  border: 1px solid var(--line); border-radius: 14px;
  text-decoration: none; color: inherit;
  transition: transform .12s ease, box-shadow .12s ease, border-color .12s ease;
}
.card:hover { transform: translateY(-2px); box-shadow: 0 6px 20px rgba(0,0,0,.07); border-color: var(--accent); }
.card:active { transform: translateY(0); }
.card.disabled { opacity: .62; }
.card.disabled:hover { transform: none; box-shadow: none; border-color: var(--line); }
.ctxt { flex: 1; min-width: 0; }
.ctxt h2 { margin: 0 0 3px; font-size: 18px; }
.ctxt p { margin: 0; font-size: 13px; color: var(--muted); }
.ctxt .note { margin-top: 5px; font-size: 12px; color: var(--muted); opacity: .85; }
.count {
  flex: none; font-size: 12px; font-weight: 700; color: var(--accent);
  background: var(--accent-soft); border-radius: 999px; padding: 5px 11px; white-space: nowrap;
}
.count.soon { color: var(--muted); background: transparent; border: 1px solid var(--line); }

.ico { flex: none; width: 46px; height: 46px; border-radius: 12px; background: var(--accent-soft); position: relative; }
.ico::after {
  content: ""; position: absolute; inset: 0; margin: auto;
  background: var(--accent); opacity: .9;
}
.ico-threads::after {
  width: 20px; height: 20px; border-radius: 50%;
  background: transparent; border: 2.6px solid var(--accent); border-right-color: transparent;
}
.ico-video::after {
  width: 0; height: 0; background: transparent;
  border-left: 15px solid var(--accent); border-top: 9px solid transparent; border-bottom: 9px solid transparent;
  transform: translateX(2px);
}

/* lesson list */
.lessons { list-style: none; margin: 0; padding: 0; background: var(--panel); border: 1px solid var(--line); border-radius: 14px; overflow: hidden; }
.lessons li + li { border-top: 1px solid var(--line); }
.lessons a {
  display: flex; align-items: center; gap: 12px;
  padding: 14px 16px; text-decoration: none; color: inherit; font-weight: 500;
}
.lessons a:hover { background: var(--accent-soft); }
.lessons .n {
  flex: none; width: 24px; height: 24px; border-radius: 7px;
  display: grid; place-items: center;
  font-size: 12px; font-weight: 700; color: var(--accent); background: var(--accent-soft);
}

/* lesson body */
.doc { background: var(--panel); border: 1px solid var(--line); border-radius: 14px; padding: 24px 22px; }
.doc h1 { margin: 0 0 20px; font-size: 23px; line-height: 1.45; }
.doc h2 { margin: 30px 0 10px; font-size: 17px; padding-bottom: 7px; border-bottom: 2px solid var(--accent-soft); }
.doc h3 { margin: 22px 0 8px; font-size: 15px; }
.doc p { margin: 12px 0; }
.doc ul, .doc ol { padding-left: 1.4em; }
.doc li { margin: 6px 0; }
.doc strong { color: var(--ink); background: linear-gradient(transparent 62%, var(--accent-soft) 62%); }
.doc code {
  font-family: ui-monospace, SFMono-Regular, Menlo, monospace; font-size: .89em;
  background: var(--accent-soft); padding: 2px 6px; border-radius: 5px;
}
.doc pre {
  background: var(--accent-soft); border: 1px solid var(--line); border-radius: 10px;
  padding: 14px 16px; overflow-x: auto;
}
.doc pre code { background: none; padding: 0; }
.doc blockquote { margin: 14px 0; padding: 2px 0 2px 14px; border-left: 3px solid var(--accent); color: var(--muted); }
.doc hr { border: 0; border-top: 1px solid var(--line); margin: 26px 0; }
.doc table { width: 100%; border-collapse: collapse; margin: 16px 0; font-size: 14px; }
.doc th, .doc td { border: 1px solid var(--line); padding: 8px 10px; text-align: left; vertical-align: top; }
.doc th { background: var(--accent-soft); font-weight: 700; }
.tablewrap { overflow-x: auto; }

.pager { display: flex; justify-content: space-between; gap: 12px; margin-top: 20px; }
.pager a {
  flex: 1; padding: 13px 15px; background: var(--panel);
  border: 1px solid var(--line); border-radius: 11px;
  text-decoration: none; color: var(--accent); font-weight: 600; font-size: 13px;
}
.pager a:hover { border-color: var(--accent); }
.pager .next { text-align: right; }

.foot { padding: 22px 16px 34px; text-align: center; color: var(--muted); font-size: 12px; }

@media (max-width: 420px) {
  .doc { padding: 18px 15px; }
  .hero h1 { font-size: 22px; }
  .pager { flex-direction: column; }
  .pager .next { text-align: left; }
}

/* ---- login / logout ---- */
.bar .logout { margin-left: auto; color: var(--muted); font-size: .85rem; text-decoration: none; }
.bar .logout:hover { color: var(--accent); }
.login {
  max-width: 360px; margin: 0 auto; padding: 20px;
  background: var(--panel); border: 1px solid var(--line); border-radius: 12px;
  display: grid; gap: 14px;
}
.login label { display: grid; gap: 6px; font-size: .9rem; color: var(--muted); }
.login input {
  font: inherit; font-size: 16px; /* iOS のズーム防止 */
  padding: 10px 12px; border: 1px solid var(--line); border-radius: 8px;
  background: var(--bg); color: var(--ink);
}
.login button {
  font: inherit; font-weight: 700; padding: 12px; border: 0; border-radius: 8px;
  background: var(--accent); color: var(--panel); cursor: pointer;
}
.login .err { margin: 0; color: var(--warn); font-weight: 600; }