.learn-page { padding: 64px 0 96px; }
.learn-page .learn-grid { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.learn-stats { display: flex; flex-wrap: wrap; align-items: center; gap: 10px; margin-top: 18px; font-size: .85rem; color: var(--text-secondary); }
.learn-stats strong { color: var(--text-primary); font-family: var(--font-mono); }
.learn-stats-sep { color: var(--border-subtle); }
.learn-card-meta { display: block; font: 600 .74rem var(--font-mono); letter-spacing: .02em; color: var(--text-muted); margin: -10px 0 12px; }
.learn-topic-list { display: grid; gap: 14px; max-width: 860px; }
.learn-topic { display: flex; align-items: center; gap: 16px; padding: 20px 22px; border: 1px solid var(--border-subtle); border-radius: 14px; background: var(--bg-surface); color: var(--text-primary); text-decoration: none; transition: border-color .2s ease, transform .2s ease, box-shadow .2s ease; }
.learn-topic:hover { border-color: var(--accent-cyan); transform: translateX(4px); box-shadow: var(--shadow-sm); }
.learn-topic-number { color: var(--accent-cyan); font: 600 .8rem var(--font-mono); }
.learn-topic-arrow { margin-left: auto; color: var(--accent-cyan); }
@media (max-width: 900px) { .learn-page .learn-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); } }
@media (max-width: 620px) { .learn-page { padding: 44px 0 64px; } .learn-page .learn-grid { grid-template-columns: 1fr; } }

/* ===== Course overview (chapter list) ===== */
.course-hero { padding: 48px 0 8px; }
.course-hero .container { max-width: 900px; }
.course-progress-summary { display: flex; align-items: center; gap: 14px; margin-top: 22px; }
.course-progress-bar { flex: 1; height: 8px; border-radius: 99px; background: var(--bg-elevated); overflow: hidden; }
.course-progress-fill { height: 100%; border-radius: 99px; background: linear-gradient(90deg, var(--accent-cyan), var(--accent-violet)); width: 0%; transition: width .4s ease; }
.course-progress-label { font-size: .82rem; font-weight: 600; color: var(--text-secondary); white-space: nowrap; font-family: var(--font-mono); }

.chapter-list { max-width: 900px; margin: 32px auto 0; padding: 0 24px 96px; display: grid; gap: 12px; }
.chapter-row { display: flex; align-items: center; gap: 18px; padding: 18px 22px; border: 1px solid var(--border-subtle); border-radius: 14px; background: var(--bg-surface); text-decoration: none; color: var(--text-primary); transition: border-color .2s ease, transform .2s ease, box-shadow .2s ease; }
.chapter-row:hover { border-color: var(--accent-cyan); transform: translateX(4px); box-shadow: var(--shadow-sm); }
.chapter-row-num { flex: 0 0 40px; height: 40px; border-radius: 50%; display: flex; align-items: center; justify-content: center; font: 700 .95rem var(--font-mono); background: var(--bg-elevated); color: var(--text-secondary); }
.chapter-row.is-done .chapter-row-num { background: var(--accent-green); color: #fff; }
.chapter-row-body { flex: 1; min-width: 0; }
.chapter-row-title { display: block; font-weight: 600; font-size: 1rem; margin-bottom: 3px; }
.chapter-row-desc { display: block; font-size: .84rem; color: var(--text-secondary); }
.chapter-row-check { flex: 0 0 auto; font-size: .78rem; font-weight: 600; color: var(--accent-green); opacity: 0; }
.chapter-row.is-done .chapter-row-check { opacity: 1; }

/* ===== Chapter page ===== */
.chapter-page { padding: 0 0 40px; }
.chapter-hero { padding-bottom: 28px; }
.chapter-kicker { font: 600 .78rem var(--font-mono); letter-spacing: .06em; text-transform: uppercase; color: var(--accent-cyan); margin-bottom: 10px; }
.chapter-hero h1 { font-size: clamp(1.6rem, 3.4vw, 2.3rem); margin-bottom: 10px; }
.chapter-hero .page-desc { max-width: 680px; }

.chapter-body-layout { display: grid; grid-template-columns: minmax(0, 1fr) 240px; gap: 48px; max-width: 1080px; margin: 0 auto; padding: 40px 24px 0; align-items: start; }
.chapter-content { min-width: 0; max-width: 680px; }
.chapter-content h2 { font-size: 1.4rem; margin: 40px 0 14px; }
.chapter-content h2:first-child { margin-top: 0; }
.chapter-content p { color: var(--text-secondary); line-height: 1.75; margin-bottom: 16px; }
.chapter-content ul, .chapter-content ol { color: var(--text-secondary); line-height: 1.75; margin: 0 0 16px; padding-left: 22px; }
.chapter-content li { margin-bottom: 6px; }
.chapter-content strong { color: var(--text-primary); }
.chapter-content code { font-family: var(--font-mono); font-size: .85em; background: var(--bg-elevated); padding: 2px 6px; border-radius: 4px; }

.chapter-diagram { margin: 24px 0 32px; padding: 24px; border: 1px solid var(--border-subtle); border-radius: 16px; background: var(--bg-surface); }
.chapter-diagram svg { width: 100%; height: auto; display: block; }
.chapter-diagram-caption { margin-top: 14px; font-size: .82rem; color: var(--text-muted); text-align: center; }

.chapter-callout { display: flex; gap: 14px; padding: 18px 20px; border-radius: 14px; background: rgba(8, 145, 178, .07); border: 1px solid rgba(8, 145, 178, .18); margin: 24px 0; }
.chapter-callout-icon { flex: 0 0 auto; font-size: 1.3rem; }
.chapter-callout p { margin: 0; color: var(--text-primary); font-size: .92rem; line-height: 1.65; }

.chapter-mark-done { display: inline-flex; align-items: center; gap: 8px; margin-top: 40px; padding: 12px 22px; border-radius: 99px; border: 1px solid var(--border-subtle); background: var(--bg-surface); color: var(--text-primary); font-weight: 600; font-size: .9rem; cursor: pointer; transition: all .2s ease; }
.chapter-mark-done:hover { border-color: var(--accent-green); }
.chapter-mark-done.is-done { background: var(--accent-green); border-color: var(--accent-green); color: #fff; }

.chapter-nav-strip { display: flex; justify-content: space-between; gap: 16px; max-width: 680px; margin: 40px 0 0; padding-top: 28px; border-top: 1px solid var(--border-subtle); }
.chapter-nav-link { flex: 1; display: flex; flex-direction: column; gap: 4px; padding: 16px 18px; border: 1px solid var(--border-subtle); border-radius: 12px; text-decoration: none; color: var(--text-primary); transition: border-color .2s ease; max-width: 300px; }
.chapter-nav-link:hover { border-color: var(--accent-cyan); }
.chapter-nav-link.next { text-align: right; margin-left: auto; }
.chapter-nav-dir { font-size: .72rem; text-transform: uppercase; letter-spacing: .05em; color: var(--text-muted); font-weight: 600; }
.chapter-nav-title { font-size: .88rem; font-weight: 600; }

.chapter-toc { position: sticky; top: 84px; }
.chapter-toc h4 { font-size: .78rem; text-transform: uppercase; letter-spacing: .05em; color: var(--text-muted); margin-bottom: 12px; }
.chapter-toc-list { display: flex; flex-direction: column; gap: 2px; list-style: none; margin: 0 0 20px; padding: 0; }
.chapter-toc-list a { display: flex; align-items: center; gap: 10px; padding: 7px 10px; border-radius: 8px; font-size: .82rem; color: var(--text-secondary); text-decoration: none; }
.chapter-toc-list a:hover { background: var(--bg-elevated); color: var(--text-primary); }
.chapter-toc-list a.current { background: var(--bg-elevated); color: var(--accent-cyan); font-weight: 600; }
.chapter-toc-list .toc-num { flex: 0 0 20px; height: 20px; border-radius: 50%; background: var(--bg-elevated); display: flex; align-items: center; justify-content: center; font: 600 .68rem var(--font-mono); color: var(--text-muted); }
.chapter-toc-list a.done .toc-num { background: var(--accent-green); color: #fff; }
.chapter-toc-cta { padding: 18px; border-radius: 14px; background: var(--bg-elevated); }
.chapter-toc-cta p { font-size: .82rem; color: var(--text-secondary); margin: 0 0 12px; line-height: 1.5; }
.chapter-toc-cta a { display: block; text-align: center; padding: 10px; border-radius: 10px; background: var(--text-primary); color: #fff; font-size: .82rem; font-weight: 600; text-decoration: none; }

@media (max-width: 860px) {
  .chapter-body-layout { grid-template-columns: 1fr; }
  .chapter-toc { position: static; order: -1; padding: 16px; border: 1px solid var(--border-subtle); border-radius: 14px; }
}
@media (max-width: 560px) {
  .chapter-nav-strip { flex-direction: column; }
  .chapter-nav-link.next { text-align: left; margin-left: 0; }
}