:root{color-scheme:dark;--bg:#11110e;--panel:#191915;--ink:#eee6d2;--muted:#bbb19b;--gold:#d6b663;--line:#49402b;--sans:system-ui,"Noto Sans CJK SC","Microsoft YaHei",sans-serif;--serif:"Noto Serif CJK SC","Songti SC",serif}
*{box-sizing:border-box}body{margin:0;background:radial-gradient(ellipse at top right,#272119,var(--bg) 62%);color:var(--ink);font:16px/1.8 var(--sans)}a{color:var(--gold);text-decoration:none}a:hover{text-decoration:underline}button,input,textarea,select{font:inherit}button,a.button{cursor:pointer}button,.button,select{border:1px solid var(--line);border-radius:9px;background:#201d16;color:var(--ink);padding:.65rem 1rem;min-height:44px}button:hover,.button:hover{border-color:var(--gold);text-decoration:none}button:disabled{opacity:.5;cursor:not-allowed}.primary{background:var(--gold);color:#18150f;border-color:var(--gold);font-weight:650}a:focus-visible,button:focus-visible,textarea:focus-visible,select:focus-visible,input:focus-visible{outline:3px solid var(--gold);outline-offset:3px}.wrap{max-width:1140px;margin:auto;padding:26px 24px 70px}.brandbar{display:flex;justify-content:space-between;gap:20px;border-bottom:1px solid var(--line);padding-bottom:14px;font-size:14px}.hero{display:grid;grid-template-columns:140px 1fr;gap:28px;align-items:center;margin:30px 0}.hero img{width:140px;aspect-ratio:19/25;object-fit:cover;border:1px solid var(--line);border-radius:3px;box-shadow:0 12px 35px #0008}.eyebrow{color:var(--gold);font-size:13px;letter-spacing:.1em}h1{font:600 clamp(24px,3.5vw,38px)/1.5 var(--serif);margin:5px 0 10px}h2{font:600 24px/1.5 var(--serif);margin:.25em 0 .6em}h3{font-size:18px;margin:0 0 .5em}.muted,.small{color:var(--muted)}.small{font-size:13px}.tabs{display:grid;grid-template-columns:repeat(3,1fr);gap:10px;margin:22px 0}.tabs a{padding:15px;text-align:center;border:1px solid var(--line);border-radius:9px}.tabs a[aria-current=page]{border-color:var(--gold);background:var(--gold);color:#17140e;font-weight:700}.summary{margin:18px 0;color:var(--muted)}.layout{display:grid;grid-template-columns:260px 1fr;gap:28px;align-items:start}aside{position:sticky;top:12px;max-height:85vh;overflow:auto;scrollbar-width:thin}details{border-bottom:1px solid var(--line);padding:8px 0}summary{cursor:pointer;color:var(--gold)}.lesson-link{display:block;padding:8px 10px;color:var(--muted);font-size:14px;border-radius:5px}.lesson-link[aria-current=true]{color:var(--ink);background:#302919;border-left:3px solid var(--gold)}.panel{background:var(--panel);border:1px solid var(--line);border-radius:14px;padding:24px;margin-bottom:18px;min-width:0}.prompt{font-size:18px;line-height:1.95}.row{display:flex;flex-wrap:wrap;align-items:center;gap:10px;margin:12px 0}label.field{display:block;margin:15px 0 6px;color:var(--ink);font-weight:550}textarea,input[type=text],input[type=password]{width:100%;background:#0e100e;border:1px solid #575044;border-radius:8px;color:var(--ink);padding:12px;line-height:1.8}textarea{min-height:115px;resize:vertical}input[type=checkbox]{width:18px;height:18px;accent-color:var(--gold);vertical-align:middle;margin-right:8px}.preserved,.reply-text{white-space:pre-wrap;overflow-wrap:anywhere;line-height:1.9}.preserved{padding:15px;border-left:2px solid var(--gold);background:#100f0d}.badge{font-size:12px;border:1px solid var(--line);padding:3px 7px;border-radius:5px;color:var(--gold)}.notice{border-left:3px solid var(--gold);padding:8px 14px;margin:12px 0;font-size:14px;color:var(--muted)}#status{position:sticky;bottom:12px;padding:10px 16px;background:#302817;border:1px solid var(--gold);border-radius:8px;z-index:3;display:none;white-space:pre-wrap;overflow-wrap:anywhere}#status.on{display:block}dialog{background:#181813;color:var(--ink);border:1px solid var(--gold);border-radius:14px;width:min(820px,94vw);max-height:92vh;padding:24px}dialog::backdrop{background:#000b}dialog textarea{min-height:250px;font-family:var(--sans);font-size:13px}pre{white-space:pre-wrap;overflow-wrap:anywhere;font:13px/1.7 var(--sans);background:#0e100e;padding:14px;border-radius:8px}.source-note{font-size:13px;overflow-wrap:anywhere}.reply{border-top:1px solid var(--line);padding:18px 0}.reply:first-child{border:0}footer{font-size:13px;color:var(--muted);border-top:1px solid var(--line);padding-top:20px;margin-top:25px}.mobile-select{display:none}.history{font-size:14px}.footlinks{display:flex;gap:20px;flex-wrap:wrap}.download{display:inline-block;margin:6px 8px 6px 0}[hidden]{display:none!important}.task-modes{display:grid;grid-template-columns:repeat(3,1fr);gap:8px}.task-modes button[aria-pressed=true]{border-color:var(--gold);background:#393019;color:var(--gold)}.print-only{display:none}@media(max-width:760px){.wrap{padding:18px 15px 55px}.hero{grid-template-columns:88px 1fr;gap:16px;margin:23px 0}.hero img{width:88px}.hero .eyebrow{font-size:11px}h1{font-size:24px}.tabs a{padding:11px 4px;font-size:14px}.layout{display:block}aside{display:none}.mobile-select{display:block;width:100%;margin:12px 0}.panel{padding:18px}.task-modes{grid-template-columns:repeat(2,1fr)}.prompt{font-size:17px}.brandbar{font-size:12px}dialog{padding:18px}.hero .small{font-size:12px}}@media print{body{background:white;color:black}.tabs,aside,button,.row,#status,dialog{display:none}.layout{display:block}.panel{break-inside:avoid;background:white;border:1px solid #aaa}.wrap{padding:0}.print-only{display:block}a,.muted,.small{color:#333}}

#status{position:fixed;left:50%;transform:translateX(-50%);width:min(820px,92vw);bottom:12px}#payload{max-height:300px;overflow:auto}#preview-error:empty{display:none}.error{color:#ffd6cc}

/* mobile cover and non-overlapping status */
.hero img{height:auto;object-fit:contain}.row.download{display:flex;gap:10px;align-items:stretch}.row.download>a,.row.download>label{display:inline-flex;align-items:center;padding:8px 12px;border:1px solid var(--line);border-radius:9px;min-height:44px;cursor:pointer}
#status{position:static;left:auto;transform:none;width:auto;margin:12px 0}.lesson-link.active{color:var(--ink);background:#302919;border-left:3px solid var(--gold)}

/* Astronomy v1.1: night navigation, paper reading, gold emphasis. */
:root{--bg:#081626;--panel:#10263d;--ink:#edf2f7;--muted:#b8c6d6;--gold:#e6c27c;--line:#344b63;color-scheme:dark}
body{background:radial-gradient(ellipse at 80% 0,#183954 0,#081626 65%)}
.book-emblem{width:140px;min-height:184px;border:1px solid #bd9654;border-radius:4px;display:flex;flex-direction:column;justify-content:center;align-items:center;background:linear-gradient(145deg,#173b59,#071a2d);box-shadow:0 12px 35px #0005;text-align:center;color:var(--gold)}.book-emblem span{font-size:42px;line-height:1.3}.book-emblem small{font:600 22px/1.7 var(--serif);letter-spacing:.15em}
button,.btn,select{background:#15314c;color:var(--ink)}button.primary{background:var(--gold);color:#152538}textarea,input[type=password],input[type=text],input[type=search]{background:#081a2b;color:var(--ink);border:1px solid #526b82;border-radius:8px;padding:12px;width:100%;min-width:0}select{max-width:100%;width:100%}.row>.field{flex:1;min-width:180px}.content{min-width:0}.lesson-link.active,.lesson-link[aria-current=true]{background:#1d3c57;border-color:var(--gold)}.source-reader{margin:20px 0;border:1px solid #cabb9e;border-radius:10px;overflow:hidden;background:#fbf7ee;color:#243447}.source-reader summary{padding:12px 16px;background:#eee5d5;color:#62491c}.source-reader .preserved{padding:24px;background:#fbf7ee;border:0;font-family:var(--serif);font-size:18px;line-height:2;max-height:70vh;overflow:auto;color:#243447}.task-guide{border-left:3px solid var(--gold);padding-left:18px;margin:22px 0}.task-guide h3{color:var(--gold);font-size:15px}.task-guide .preserved{padding:0;background:none;border:0}.knowledge{margin:16px 0}.preserved{background:#0a1d30}.knowledge .preserved{font-size:14px}pre{background:#071b2d}dialog{background:#10263d}#status{background:#17334e}.notice{color:var(--muted)}.error{color:#ffd2be}.landing-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:18px}.landing-grid .panel{display:flex;flex-direction:column;gap:8px}.landing-grid .btn{display:inline-block;padding:12px;border:1px solid var(--line);border-radius:8px;margin-top:auto}.lead{max-width:750px;font-size:19px}.landing-hero{padding:42px 0}.footlinks p{flex-basis:100%}.source-reader .preserved:focus-visible{outline:3px solid #8f6a20}.mobile-select{display:none!important}input[type=search]{font:inherit}#task-search{font-size:14px}.source-reader a{color:#765419}
@media(max-width:760px){.book-emblem{width:88px;min-height:120px}.book-emblem span{font-size:30px}.book-emblem small{font-size:16px}.landing-grid{grid-template-columns:1fr}.mobile-select{display:block!important}.source-reader .preserved{padding:16px;font-size:17px}.row>.field{min-width:100%}.hero p{font-size:14px}.tabs{gap:5px}}
@media print{.source-reader .preserved{max-height:none;overflow:visible}.panel,.preserved{background:white;color:black}.task-guide h3,summary{color:black}.knowledge{display:none}}