/* Reuse existing course typography, tables, callouts and brand colors. */
.section-lesson { max-width: 900px; }
.section-lesson .section-lead { font-size: 19px; line-height: 1.65; }
.section-lesson .section-equation { display: block; overflow-wrap: anywhere; font-family: Georgia, "Times New Roman", serif; font-size: 20px; }
.section-table { min-width: 480px; }
.section-figure svg { color: var(--course-ink); font-family: "Open Sans", system-ui, sans-serif; }
.section-lesson details { margin: 24px 0; border: 1px solid #e2e8f0; border-radius: 14px; padding: 18px 20px; background: #fff; }
.section-lesson summary { cursor: pointer; color: #1f4e4f; font-weight: 700; }
.section-lesson details[open] summary { margin-bottom: 18px; }
.section-lesson details p:last-child { margin-bottom: 0; }
.section-explorer { margin: 28px 0; border: 1px solid #e2e8f0; border-radius: 16px; padding: 20px; background: #f8fafc; }
.section-explorer button, .section-print-button { min-height: 44px; padding: 10px 14px; border: 1px solid #2f7a7b; border-radius: 9px; color: #1f4e4f; background: #fff; font: inherit; font-size: 14px; font-weight: 700; cursor: pointer; }
.section-explorer button[aria-pressed=true] { color: #fff; background: var(--course-brand); }
.section-explorer input[type=range] { display: block; width: 100%; max-width: 440px; min-height: 44px; accent-color: var(--course-brand); }
.section-explorer output { display: block; margin-top: 18px; font-weight: 600; }
.section-shell { max-width: 1100px; margin: 0 auto; padding: 40px 24px 64px; }
.section-shell h1 { margin: 16px 0 24px; color: var(--course-ink); font-size: clamp(2rem, 4vw, 3rem); font-weight: 800; line-height: 1.2; }
.section-shell .section-lesson { max-width: none; }
.section-actions { display: flex; flex-wrap: wrap; gap: 12px; margin: 28px 0; }
.section-actions a { display: inline-flex; align-items: center; padding: 10px 14px; border: 1px solid #2f7a7b; border-radius: 9px; color: #1f4e4f; font-size: 14px; font-weight: 800; text-decoration: none; }
.section-actions a:first-child { color: #fff; background: var(--course-brand); }
.section-actions a:hover { background: #ecfbfb; }
.section-actions a:first-child:hover { background: #1f4e4f; }
.section-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 18px; }
.section-card { padding: 22px; border: 1px solid #e2e8f0; border-radius: 16px; background: #fff; }
.section-card h2 { margin: 8px 0 12px; font-size: 20px; }
.section-card p:last-child { margin-bottom: 0; }
.section-small { color: #64748b; font-size: 13px; }
.section-scratch { min-height: 100px; margin: 12px 0 24px; border: 1px solid #cbd5e1; border-radius: 9px; }
.section-course-private { max-width: 1400px; margin: 0 auto 16px; padding: 14px 18px; border: 1px solid #a8eaeb; border-radius: 12px; color: #1f4e4f; background: #ecfbfb; font-size: 13px; line-height: 1.6; }
.section-lesson :focus-visible, .section-shell :focus-visible { outline: 3px solid var(--course-brand); outline-offset: 4px; }
@media (max-width: 600px) {
    .section-grid { grid-template-columns: minmax(0, 1fr); }
    .section-shell { padding: 24px 16px; }
    .section-lesson h2 { font-size: 23px; }
    .section-figure { overflow-x: auto; }
    .section-figure svg { min-width: 550px; }
    .section-explorer { padding: 16px; }
    .section-explorer button { margin: 3px 0; }
}
@media print {
    .section-actions, .section-print-button, .section-explorer button, .section-explorer input { display: none !important; }
    .section-shell { max-width: none; padding: 0; }
    .section-figure, .section-task, .section-equation, .section-card { break-inside: avoid; }
    .section-figure svg { min-width: 0; max-height: 290px; }
    .section-lesson details > :not(summary) { display: block !important; }
    .section-grid { display: block; }
    .section-card { margin: 16px 0; }
    .section-lesson h2 { break-after: avoid; }
    .section-lesson { font-size: 10.5pt; line-height: 1.5; }
    .section-notice { background: #fff; }
}