:root {
  color-scheme: light;
  --page: #f9f9f7; --surface: #ffffff; --border: rgba(11,11,11,.10);
  --ink: #14140f; --ink-2: #52514e; --muted: #898781;
  --accent: #1a5fb4; --accent-2: #eaf1fb;
  --good: #006300; --bad: #d03b3b;
}
@media (prefers-color-scheme: dark) {
  :root:where(:not([data-theme="light"])) {
    color-scheme: dark;
    --page: #0d0d0c; --surface: #1a1a18; --border: rgba(255,255,255,.10);
    --ink: #f5f5f0; --ink-2: #c3c2b7; --muted: #898781;
    --accent: #6ea8e5; --accent-2: #17263a;
    --good: #0ca30c; --bad: #e2685f;
  }
}
:root[data-theme="dark"] {
  color-scheme: dark;
  --page: #0d0d0c; --surface: #1a1a18; --border: rgba(255,255,255,.10);
  --ink: #f5f5f0; --ink-2: #c3c2b7; --muted: #898781;
  --accent: #6ea8e5; --accent-2: #17263a;
  --good: #0ca30c; --bad: #e2685f;
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0; background: var(--page); color: var(--ink);
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", system-ui, sans-serif;
  line-height: 1.7; font-size: 17px;
}
.wrap { max-width: 800px; margin: 0 auto; padding: 0 20px; }
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
img { max-width: 100%; height: auto; }

/* header */
.site-header { border-bottom: 1px solid var(--border); background: var(--surface); }
.site-header .wrap { display: flex; align-items: center; justify-content: space-between; padding: 16px 20px; max-width: 900px; }
.brand { font-weight: 800; font-size: 20px; color: var(--ink); }
.main-nav a { margin-left: 20px; font-weight: 600; color: var(--ink-2); }
.main-nav a:hover { color: var(--accent); }

/* hero */
.hero { padding: 56px 0 40px; text-align: center; }
.hero h1 { font-size: 34px; margin: 0 0 12px; }
.hero .lead { color: var(--ink-2); font-size: 18px; max-width: 560px; margin: 0 auto; }

/* course grid */
.course-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); gap: 20px; padding-bottom: 60px; max-width: 900px; }
.course-card {
  display: block; background: var(--surface); border: 1px solid var(--border); border-radius: 14px;
  padding: 28px; color: var(--ink);
}
.course-card:hover { border-color: var(--accent); text-decoration: none; }
.course-icon { font-size: 32px; }
.course-card h2 { margin: 10px 0 8px; font-size: 22px; }
.course-card p { color: var(--ink-2); margin: 0 0 14px; }
.course-count { font-size: 13px; color: var(--accent); font-weight: 700; }

/* breadcrumb */
.breadcrumb { padding: 18px 20px 0; font-size: 14px; color: var(--muted); }
.breadcrumb a { color: var(--muted); }

/* course index list */
h1 { font-size: 28px; }
.lead { color: var(--ink-2); }
.lesson-list { list-style: none; margin: 28px 0 60px; padding: 0; display: flex; flex-direction: column; gap: 10px; }
.lesson-list a {
  display: flex; align-items: center; gap: 14px; background: var(--surface); border: 1px solid var(--border);
  border-radius: 10px; padding: 16px 18px; color: var(--ink);
}
.lesson-list a:hover { border-color: var(--accent); text-decoration: none; }
.lesson-num { font-weight: 700; color: var(--accent); font-size: 14px; flex-shrink: 0; }
.lesson-title { flex: 1; font-weight: 600; }
.lesson-meta { color: var(--muted); font-size: 13px; flex-shrink: 0; }

/* lesson article */
.lesson { padding: 24px 20px 80px; }
.course-progress { color: var(--accent); font-weight: 700; font-size: 13px; letter-spacing: .02em; margin: 0 0 6px; }
.lesson h1 { margin-top: 0; }
.lesson-body h2 { margin-top: 40px; font-size: 22px; border-top: 1px solid var(--border); padding-top: 28px; }
.lesson-body h3 { font-size: 18px; margin-top: 28px; }
.lesson-body p { color: var(--ink); }
.lesson-body ul, .lesson-body ol { padding-left: 22px; }
.lesson-body li { margin: 6px 0; }
.lesson-body code { background: var(--accent-2); padding: 2px 6px; border-radius: 4px; font-size: 15px; }
.lesson-body pre { background: var(--accent-2); padding: 14px 16px; border-radius: 8px; overflow-x: auto; }
.lesson-body table { border-collapse: collapse; width: 100%; margin: 20px 0; font-size: 15px; }
.lesson-body th, .lesson-body td { border: 1px solid var(--border); padding: 8px 12px; text-align: left; }
.lesson-body th { background: var(--accent-2); }
.lesson-body blockquote {
  margin: 20px 0; padding: 14px 18px; background: var(--accent-2); border-left: 4px solid var(--accent);
  border-radius: 0 8px 8px 0; color: var(--ink-2);
}
.lesson-body blockquote p { margin: 0; }
.lesson-body hr { border: none; border-top: 1px solid var(--border); margin: 32px 0; }
.lesson-body figure.diagram { margin: 24px 0; text-align: center; }
.lesson-body figure.diagram img { max-width: 100%; height: auto; border-radius: 12px; }
.lesson-body figure.diagram figcaption { margin-top: 8px; font-size: 13px; color: var(--muted); }
.muted { color: var(--muted); font-size: 14px; }

/* pager */
.lesson-pager { display: flex; justify-content: space-between; gap: 16px; margin-top: 56px; padding-top: 24px; border-top: 1px solid var(--border); }
.pager-link { flex: 1; background: var(--surface); border: 1px solid var(--border); border-radius: 10px; padding: 14px 16px; color: var(--ink); }
.pager-link:hover { border-color: var(--accent); text-decoration: none; }
.pager-link span { display: block; font-size: 12px; color: var(--muted); margin-bottom: 4px; }
.pager-link.next { text-align: right; margin-left: auto; }

/* footer */
.site-footer { border-top: 1px solid var(--border); margin-top: 40px; padding: 28px 0 40px; }
.site-footer .wrap { max-width: 900px; }
.site-footer p { color: var(--muted); font-size: 13px; margin: 4px 0; }

@media (max-width: 560px) {
  body { font-size: 16px; }
  .hero h1 { font-size: 26px; }
  .lesson-pager { flex-direction: column; }
}