.lesson-page > .pb-toc,
body.mit65840-textbook > .pb-toc,
body.mit65840-workbook > .pb-toc { display: none !important; }

.active-orientation .section-lede { font-size: 1.08rem; }
.system-object-map { display: flex; align-items: stretch; gap: .55rem; margin: 1.4rem 0; overflow-x: auto; padding-bottom: .35rem; }
.system-object-map span { min-width: 120px; flex: 1; border: 1px solid var(--line, #d8d3c8); padding: .8rem .7rem; background: rgba(255,255,255,.48); font: 700 .78rem/1.35 ui-monospace, SFMono-Regular, Menlo, monospace; text-align: center; }
.system-object-map b { align-self: center; color: var(--accent, #8c4e35); }
.before-start { margin: 1.35rem 0; border-top: 1px solid var(--line, #d8d3c8); }
.before-start h3 { margin: 1.2rem 0 .45rem; }
.before-start details, .open-prompts details { border-bottom: 1px solid var(--line, #d8d3c8); padding: .75rem 0; }
.before-start summary, .open-prompts summary { cursor: pointer; font-weight: 700; }
.before-start details p, .open-prompts details p { margin: .75rem 0 .2rem; color: var(--ink-soft, #514c43); }
.mental-model { border-left: 3px solid var(--accent, #8c4e35); padding: .75rem 1rem; background: rgba(140,78,53,.055); }
.mental-model span, .assignment-bridge > span { color: var(--accent, #8c4e35); font: 800 .7rem/1.2 ui-monospace, SFMono-Regular, Menlo, monospace; letter-spacing: .1em; }
.mental-model p { margin: .35rem 0 0; font-weight: 700; }

.inline-concept-check { margin: 1.35rem 0 2rem; padding: 1rem 1.1rem; border: 1px solid var(--line, #d8d3c8); border-left: 3px solid var(--accent, #8c4e35); background: rgba(255,255,255,.42); }
.check-kicker { margin-bottom: .7rem; color: var(--accent, #8c4e35); font: 800 .68rem/1.2 ui-monospace, SFMono-Regular, Menlo, monospace; letter-spacing: .09em; text-transform: uppercase; }
.question-prompt { margin: 0 0 .8rem; }
.active-options { display: grid; gap: .55rem; }
.active-options button { display: flex; align-items: flex-start; gap: .65rem; width: 100%; border: 1px solid var(--line, #d8d3c8); background: rgba(255,255,255,.72); color: inherit; padding: .72rem .8rem; text-align: left; cursor: pointer; font: inherit; }
.active-options button span { display: grid; place-items: center; flex: 0 0 1.45rem; height: 1.45rem; border: 1px solid currentColor; font: 800 .7rem/1 ui-monospace, monospace; }
.active-options button:hover, .active-options button:focus-visible { border-color: var(--accent, #8c4e35); }
.active-options button.is-correct { border-color: #39725d; background: rgba(57,114,93,.08); }
.active-options button.is-wrong { border-color: #a05245; background: rgba(160,82,69,.08); }
.active-feedback { margin-top: .8rem; padding: 0; }
.active-feedback.is-correct, .active-feedback.is-wrong { padding: .75rem .85rem; border-left: 2px solid currentColor; }
.active-feedback.is-correct { color: #315f50; }
.active-feedback.is-wrong { color: #8b4339; }
.active-feedback p { margin: .3rem 0 0; color: var(--ink, #25221e); }
.follow-up-slot { margin-top: .9rem; padding-top: .9rem; border-top: 1px dashed var(--line, #d8d3c8); }
.follow-up-slot.is-required::before { content: 'MISCONCEPTION REPAIR · 换一个表面再验证'; display: block; margin-bottom: .7rem; color: #8b4339; font: 800 .68rem/1.2 ui-monospace, monospace; letter-spacing: .08em; }
.retry-trigger { border: 0; background: transparent; color: var(--accent, #8c4e35); padding: .25rem 0; font: 700 .86rem/1.2 inherit; cursor: pointer; }
.transfer-check { margin-top: 1.2rem; padding-top: 1rem; border-top: 1px dashed var(--line, #d8d3c8); }
.explain-yourself { margin-top: 2.4rem; }
.can-explain { margin: 1.35rem 0; padding: 1rem 1.1rem; border-top: 2px solid var(--ink, #25221e); border-bottom: 1px solid var(--line, #d8d3c8); }
.can-explain h3 { margin-top: 0; }
.can-explain ul { list-style: none; padding: 0; columns: 2; column-gap: 2rem; }
.can-explain li { break-inside: avoid; margin: .45rem 0; }
.assignment-bridge { margin-top: 1.5rem; padding: 1rem 1.1rem; border: 1px solid var(--line, #d8d3c8); }
.assignment-bridge h3 { margin: .4rem 0; }
.assignment-bridge p { margin: .3rem 0 .7rem; }
.assignment-bridge a { font-weight: 800; }

@media (max-width: 700px) {
  .can-explain ul { columns: 1; }
  .system-object-map { align-items: center; }
  .system-object-map span { min-width: 150px; }
}