/* One reading surface, with a stationary chapter index and navigation. */
body[data-screen=core]{--heading-space-scale:.49}
body[data-screen=core] .division-label,body[data-screen=core] .home-learning{display:none}
#core-view{display:flex;flex-direction:column;min-height:0;flex:1;border:1px solid var(--line);border-radius:10px;overflow:hidden;background:var(--panel);box-shadow:var(--shadow-soft)}
.core-title-actions{display:none}
body[data-screen=core] .topic-heading{column-gap:10px}
body[data-screen=core] .core-title-actions{display:flex;align-self:flex-end;gap:6px;flex:none}
.core-title-actions button{font-size:11px;min-height:32px;padding:5px 9px;white-space:nowrap}
.core-workspace{display:grid;grid-template-columns:190px minmax(0,1fr);flex:1;min-height:0}
.core-contents{background:#171a1f;border-right:1px solid var(--line);padding:14px 10px;overflow:auto;scrollbar-width:thin}
.core-contents>strong{display:block;color:#b4c5d7;font-size:11px;padding:0 9px 10px;letter-spacing:.12em}
#core-toc{display:flex;flex-direction:column;gap:5px}
#core-toc button{display:flex;gap:9px;align-items:baseline;text-align:left;border-color:transparent;background:transparent;padding:9px 8px;line-height:1.5}
#core-toc button>span{font-size:10px;color:var(--muted)}
#core-toc button>strong{font-size:12px;font-weight:550}
#core-toc button[aria-current=step]{background:#2a3542;border-color:#5c7187;box-shadow:inset 2px 0 #bdcfe2}
.core-reading{min-width:0;min-height:0;display:flex;flex-direction:column}
#core-body{flex:1;min-height:0;overflow:auto;overscroll-behavior:contain;scrollbar-width:thin;scrollbar-color:#515763 transparent}
.core-article{max-width:900px;padding:24px 32px 28px;margin:0 auto;overflow-wrap:anywhere}
.core-chapter-number{font-size:11px;letter-spacing:.1em;color:#b9a486;margin-bottom:5px}
.core-article h2{font-size:26px;line-height:1.35;letter-spacing:-.7px;margin:0 0 12px}
.core-article p,.core-article li{font-size:14px;line-height:1.8}
.core-article p{margin:10px 0 15px}
.core-article .core-lead{font-size:16px;line-height:1.65;color:#d7e2ef;font-weight:600;margin:0 0 14px}
.core-intro{color:var(--muted);border-left:2px solid #61738a;padding-left:14px}
.core-article h3{font-size:15px;margin:0 0 10px;color:#d1ddeb}
.core-practice,.core-corrections,.core-check{padding:17px 18px;margin:20px 0;border-radius:8px;background:#20262f;border:1px solid #303a47}
.core-practice ol,.core-check ul{padding-left:21px;margin:0}
.core-article li{padding-left:3px;margin:5px 0}
.core-corrections{background:#27241f;border-color:#443b2e}
.core-corrections h3{color:#e1c79e}.core-correction+.core-correction{border-top:1px solid #494035;padding-top:12px;margin-top:12px}
.core-correction h4{font-size:14px;margin:0}.core-correction p{margin:5px 0}
.core-correction .core-why{color:#b8b2a9;font-size:12px}
.core-check{background:#212532}.core-check h3{color:#c9c5e7}
.core-sources{border-top:1px solid var(--line);padding-top:12px;margin-top:24px;font-size:11px;color:var(--muted)}
.core-sources summary{cursor:pointer;min-height:32px}.core-sources p{font-size:11px;line-height:1.6;margin:8px 0}.core-sources small{display:block;font-size:10px;color:var(--muted)}
.core-footer{display:flex;align-items:center;justify-content:space-between;gap:8px;border-top:1px solid var(--line);padding:7px 16px;flex:none;background:#1c2027}
.core-footer button{min-height:36px;font-size:12px;padding:6px 12px}.core-footer span{font-size:11px;color:var(--muted)}
#core-chapter-select{display:none}.core-article .lesson-photo-grid{margin:20px 0}.core-article .posture-frame{margin:20px 0;max-width:640px}
.course-card .course-entry{grid-column:1/-1;display:flex;gap:6px;margin-top:12px;flex-wrap:wrap}
.course-card .course-description{display:-webkit-box;-webkit-box-orient:vertical;-webkit-line-clamp:2;overflow:hidden}
.course-entry button{font-size:11px;min-height:34px;padding:6px 8px}.course-entry button:first-child{background:#2c3948;border-color:#4c617a}
.course-card:has(.course-entry){cursor:default}.course-card:has(.course-entry):hover{transform:none}
#open-core{font-size:12px;white-space:nowrap;margin-left:auto;min-height:36px;padding:6px 10px}
@media(min-width:761px){body[data-screen=core] #mobile-topic{display:none}}
@media(max-width:1100px){.core-workspace{grid-template-columns:166px minmax(0,1fr)}.core-article{padding:20px 24px}}
@media(max-width:760px){.core-workspace{display:flex;flex-direction:column}.core-contents{display:none}#core-chapter-select{display:block;width:100%;border:0;border-bottom:1px solid var(--line);border-radius:0;background:#202833;min-height:42px;font-size:12px}.core-reading{flex:1}.core-article{padding:18px 20px}.core-article h2{font-size:23px}body[data-screen=core] .topic-title-group>div{display:none}body[data-screen=core] #mobile-topic{display:block;min-width:0;max-width:none;flex:1;margin:0}body[data-screen=core] .topic-heading{column-gap:6px;flex-wrap:nowrap}body[data-screen=core] #mobile-topic{width:0}.core-title-actions button{font-size:10px;min-height:36px;padding:5px 7px}.core-title-actions{gap:4px}}
@media(max-width:600px){.core-article{padding:16px}.core-article h2{font-size:22px}.core-article p,.core-article li{font-size:13px;line-height:1.75}.core-article .core-lead{font-size:14px}.core-practice,.core-corrections,.core-check{padding:13px;margin:16px 0}.core-footer{padding:6px 10px}.core-article .lesson-photo-single{max-width:none}#open-core{font-size:10px;padding:6px 8px}.course-card .course-entry{gap:5px}.course-entry button{font-size:10px}}
@media(max-height:550px){.core-article{padding-top:15px}.core-footer{padding-block:4px}}