:root{color-scheme:light;--paper:#f7f6ef;--white:#fffefa;--ink:#162f2b;--muted:#4f635a;--line:#d6dacf;--green:#245848;--lime:#dcf1af;--font:"Microsoft YaHei UI","PingFang SC","Noto Sans CJK SC",sans-serif}
*{box-sizing:border-box}
body{margin:0;background:var(--paper);color:var(--ink);font:15px/1.6 var(--font)}
a{color:inherit}
[hidden]{display:none!important}
button,input{font:inherit}
button{cursor:pointer}
button:disabled{cursor:default;opacity:.45}
button:focus-visible,a:focus-visible,input:focus-visible,summary:focus-visible{outline:2px solid #517534;outline-offset:4px}
.site-header{display:flex;justify-content:space-between;align-items:center;gap:1rem;padding:.8rem max(5vw,calc((100vw - 1320px)/2));border-bottom:1px solid var(--line);background:var(--white)}
.brand{display:inline-flex;align-items:center;gap:.75rem;font-weight:700;text-decoration:none;white-space:nowrap}
.brand-mark{display:grid;place-items:center;width:2.1rem;height:2.1rem;background:var(--green);color:var(--lime);border-radius:.35rem;font-size:1rem}
.header-actions{display:flex;align-items:center;justify-content:flex-end;gap:.85rem}
#video-status{font-size:.78rem;color:var(--muted)}
.utility,.controls button,.dialog-head button{border:1px solid var(--line);border-radius:.4rem;background:var(--white);color:var(--ink);padding:.35rem .72rem;white-space:nowrap}
.utility:hover,.dialog-head button:hover{background:var(--lime)}
main{width:min(1320px,90%);margin:0 auto 4rem}
.intro{display:flex;justify-content:space-between;align-items:end;gap:1.5rem;padding:clamp(2rem,6.5vw,6rem) 0 2.1rem;border-bottom:1px solid var(--line)}
.eyebrow{margin:0 0 .4rem;color:var(--green);font-size:.83rem;letter-spacing:.12em;font-weight:700}
h1{margin:0;font-size:clamp(2.2rem,7vw,5rem);line-height:1.14;letter-spacing:-.045em}
.summary{color:var(--muted);margin:.85rem 0 0}
.search{display:grid;gap:.3rem;min-width:min(100%,16rem);color:var(--muted);font-size:.86rem}
.search input{width:100%;border:1px solid var(--line);border-radius:.45rem;background:var(--white);padding:.68rem .85rem;color:var(--ink)}
.tabs{display:flex;gap:.6rem;margin:1.45rem 0 2rem}
.tabs button{border:1px solid var(--line);background:transparent;border-radius:100vw;padding:.34rem .9rem;color:var(--ink)}
.tabs button[aria-pressed=true]{background:var(--green);color:white;border-color:var(--green)}
.chapter{margin:0 0 2.4rem}
.chapter h2{font-size:1.13rem;margin:0 0 .85rem;display:flex;gap:.65rem;align-items:baseline}
.chapter h2 span{font-size:.77rem;color:var(--green)}
.cards{display:grid;grid-template-columns:repeat(auto-fill,minmax(min(100%,240px),1fr));gap:1rem}
.card{display:flex;flex-direction:column;overflow:hidden;text-decoration:none;border:1px solid var(--line);border-radius:.65rem;background:var(--white)}
.card:hover{border-color:var(--green)}
.card img{width:100%;height:auto;aspect-ratio:16/9;object-fit:contain;display:block;background:#e8ece4;border-bottom:1px solid var(--line)}
.card-body{padding:.77rem .9rem .86rem;display:flex;flex-direction:column;gap:.25rem}
.card-title{font-size:.98rem;font-weight:700;line-height:1.45}
.card-meta,.reader-top span{color:var(--muted);font-size:.82rem}
#reader{max-width:1130px}
.reader-top{display:flex;justify-content:space-between;align-items:center;margin:1.35rem 0 .9rem;gap:.75rem}
.reader-top a{font-weight:700;text-decoration:none}
.reader-top a:hover{text-decoration:underline}
#lesson-title{font-size:clamp(1.5rem,4.2vw,2.85rem);margin-bottom:1rem}
.viewer{overflow:hidden;background:#132420;border-radius:.65rem}
.stage{position:relative;aspect-ratio:16/9;display:grid;place-items:center;overflow:hidden;background:#101917}
.stage img{position:absolute;inset:0;width:100%;height:100%;object-fit:contain;min-height:0;min-width:0}
.controls{display:flex;justify-content:center;align-items:center;gap:.65rem;padding:.75rem;color:white}
.controls button{background:transparent;color:white;border-color:#52675f}
.controls button:not(:disabled):hover{background:#31554b}
.page-control{display:flex;gap:.45rem;align-items:center;white-space:nowrap}
.page-control input{width:3rem;text-align:center;background:#f7f6ef;color:var(--ink);border:0;border-radius:.22rem;padding:.25rem 0;appearance:textfield}
.page-control input::-webkit-inner-spin-button,.page-control input::-webkit-outer-spin-button{appearance:none;margin:0}
.viewer:fullscreen{border-radius:0;display:flex;flex-direction:column}
.viewer:fullscreen .stage{flex:1;aspect-ratio:auto;min-height:0}
.reader-details{margin:.8rem 0;display:grid;gap:.5rem}
details{border:1px solid var(--line);border-radius:.4rem;background:var(--white);padding:.5rem .75rem}
summary{cursor:pointer;font-weight:600}
#slide-copy p{margin:.3rem 0}
#outline-items{display:flex;flex-wrap:wrap;gap:.4rem;margin-top:.6rem}
#outline-items button,.asset-list button,.asset-list a{border:1px solid var(--line);border-radius:.35rem;background:var(--white);color:var(--ink);padding:.32rem .65rem;text-decoration:none}
#outline-items button[aria-current=page],#outline-items button:hover,.asset-list button:hover,.asset-list a:hover{background:var(--lime)}
.resources{margin-top:1.35rem}
.resources h2{font-size:1.13rem;margin:0 0 .6rem}
.asset-list{display:flex;gap:.5rem;flex-wrap:wrap}
.asset-list small{margin-right:.55em;color:var(--green);font-weight:700}
dialog{width:min(880px,92vw);padding:1rem 1.2rem;border:1px solid var(--line);border-radius:.7rem;background:var(--white);color:var(--ink)}
dialog::backdrop{background:#0d211ed9}
.dialog-head{display:flex;align-items:center;justify-content:space-between;gap:1rem}
.dialog-head h2{margin:0;font-size:1.15rem}
#asset-body{margin-top:.85rem}
#asset-body video,#asset-body img{display:block;max-height:72vh;max-width:100%;margin:auto}
#asset-body video{width:100%;background:#131e1b}
.sr{position:absolute;width:1px;height:1px;overflow:hidden;clip-path:inset(50%);white-space:nowrap}
@media(max-width:580px){.site-header{flex-wrap:wrap;gap:.5rem}.header-actions{gap:.4rem}.intro{align-items:stretch;flex-direction:column}.controls{gap:.35rem;padding:.5rem}.controls button{padding:.3rem .45rem}main{width:92%}.cards{grid-template-columns:repeat(2,minmax(0,1fr))}.card-body{padding:.6rem}.card-title{font-size:.85rem}}
@media(max-width:350px){.cards{grid-template-columns:1fr}}