:root{color-scheme:light;--bg:#fff;--ink:#171717;--muted:#666;--soft:#f2f2f2;--hover:#e9e9e9;--line:#e5e5e5;--accent:#b8470b;--accent-soft:#fff0e7;--green:#236147;--tint:#edf5ee;--sidebar:232px}
*{box-sizing:border-box;scrollbar-width:thin;scrollbar-color:#aaa transparent}body{margin:0;background:var(--bg);color:var(--ink);font:14px/1.5 Arial,Helvetica,sans-serif}body.dark{color-scheme:dark;--bg:#151515;--ink:#ededed;--muted:#aaa;--soft:#272727;--hover:#333;--line:#383838;--accent:#ff9b61;--accent-soft:#38251b;--green:#a1cfb4;--tint:#1e3025}a{color:inherit;text-decoration:none}button,input,select,textarea{font:inherit}button,a,input,select,textarea{-webkit-tap-highlight-color:transparent}button{cursor:pointer;color:var(--ink);border:0;background:var(--soft);border-radius:8px;padding:10px 16px;font-weight:600}button:hover{background:var(--hover)}button:disabled{opacity:.45;cursor:default}a:focus-visible,button:focus-visible,input:focus-visible,select:focus-visible,textarea:focus-visible{outline:2px solid var(--accent);outline-offset:3px}::selection{background:var(--accent-soft);color:var(--ink)}input,textarea{caret-color:var(--accent)}h1,h2,h3,p{margin:0}svg{width:21px;height:21px;display:block;flex-shrink:0}.hidden{display:none!important}.skip-link{position:fixed;left:15px;top:-70px;z-index:20;background:var(--ink);color:var(--bg);padding:12px}.skip-link:focus{top:10px}
.topbar{height:64px;position:fixed;top:0;left:0;right:0;display:flex;align-items:center;padding:0 24px 0 16px;gap:32px;background:var(--bg);z-index:10}.brand-group{width:200px;display:flex;align-items:center;gap:18px;flex-shrink:0}.brand{font-size:21px;font-weight:750;letter-spacing:-.035em;white-space:nowrap}.brand span{color:var(--accent)}.icon-button{display:inline-flex;align-items:center;justify-content:center;width:40px;height:40px;border-radius:50%;padding:0;background:transparent;flex-shrink:0}.icon-button:hover{background:var(--soft)}.search-form{display:flex;height:40px;max-width:640px;width:100%;margin:0 auto}.search-form input{border:1px solid var(--line);background:var(--bg);color:var(--ink);border-radius:24px 0 0 24px;padding:0 18px;min-width:0;width:100%;font-size:16px;box-shadow:inset 0 1px 2px #00000008}.search-form input::placeholder{color:var(--muted)}.search-submit{width:62px;border:1px solid var(--line);border-left:0;border-radius:0 24px 24px 0;display:grid;place-items:center;flex-shrink:0}.header-actions{display:flex;gap:8px;flex-shrink:0}.sidebar{position:fixed;top:64px;bottom:0;left:0;width:var(--sidebar);padding:8px 12px 0;background:var(--bg);z-index:9;overflow:hidden;display:flex;flex-direction:column}.nav-link{display:flex;align-items:center;gap:22px;padding:11px 14px;border-radius:10px;line-height:20px}.nav-link:hover,.nav-link.active{background:var(--soft)}.nav-link.active{font-weight:600}.nav-count{margin-left:auto;font-size:12px;background:var(--hover);border-radius:4px;padding:0 6px}.nav-divider{height:1px;background:var(--line);margin:13px 0}.nav-section-label{padding:8px 14px;font-size:12px;color:var(--muted);font-weight:600}.sidebar-bottom{display:flex;flex-wrap:wrap;gap:8px 16px;padding:26px 14px;font-size:12px;color:var(--muted);margin-top:auto}.sidebar-bottom a:hover{text-decoration:underline}main{margin-left:var(--sidebar);padding:78px 24px 56px 28px;min-height:100vh}
.topic-strip{display:flex;gap:8px;overflow-x:auto;padding:0 0 12px;scrollbar-width:none}.topic-strip::-webkit-scrollbar{display:none}.topic-chip{white-space:nowrap;font-size:13px;border-radius:8px;padding:7px 12px}.topic-chip[aria-pressed=true]{background:var(--ink);color:var(--bg)}.catalog-toolbar{display:flex;align-items:center;justify-content:space-between;gap:18px;margin:7px 0 14px;min-height:36px}.toolbar-left{display:flex;align-items:center;gap:16px;min-width:0}.filter-button{display:flex;gap:8px;align-items:center;border-radius:24px;padding:8px 14px;font-size:13px}.filter-button svg{width:18px;height:18px}#result-count{font-size:13px;color:var(--muted);font-variant-numeric:tabular-nums}.sort-control{display:flex;gap:7px;align-items:center;color:var(--muted);font-size:12px;white-space:nowrap}.sort-control select{border:0;background:var(--bg);color:var(--ink);padding:7px 3px;font-weight:600;max-width:160px}.filters{display:grid;grid-template-columns:2fr 1fr 1fr 1fr auto;align-items:end;gap:14px;padding:18px;background:var(--soft);border-radius:12px;margin-bottom:16px}.filters label{display:flex;flex-direction:column;gap:6px;font-size:12px;color:var(--muted)}.filters select{border:1px solid var(--line);background:var(--bg);color:var(--ink);border-radius:6px;padding:9px;min-width:0;max-width:100%}.text-button{background:transparent;color:var(--accent);white-space:nowrap}.material-filter-row{display:flex;align-items:center;gap:12px;margin:0 0 23px}.filter-label{font-size:12px;color:var(--muted);flex-shrink:0}.material-filters{display:flex;align-items:center;gap:7px;overflow-x:auto;padding:2px;scrollbar-width:none}.material-filter{border:1px solid var(--line);background:var(--bg);font-size:12px;padding:5px 10px;border-radius:6px;white-space:nowrap;font-weight:500}.material-filter[aria-pressed=true]{color:var(--accent);border-color:var(--accent);background:var(--accent-soft)}.material-filter .count{padding-left:5px;font-size:11px}.active-context{font-size:14px;margin:0 0 20px;padding-bottom:12px;border-bottom:1px solid var(--line)}.active-context strong{font-size:16px}.active-context .text-button{font-size:12px;margin-left:8px}
.video-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:34px 16px}.video-card{min-width:0;position:relative}.thumbnail{aspect-ratio:16/9;display:block;background:var(--soft);border-radius:12px;overflow:hidden;position:relative}.thumbnail img{width:100%;height:100%;display:block;object-fit:cover}.duration{position:absolute;right:6px;bottom:6px;color:#fff;background:#000d;padding:1px 4px;border-radius:3px;font-size:12px;font-weight:600;line-height:17px;font-variant-numeric:tabular-nums}.save-card{position:absolute;right:7px;top:7px;padding:6px;border-radius:6px;color:#fff;background:#000b;opacity:0;transition:opacity 140ms}.save-card:hover{background:#000}.save-card svg{width:18px;height:18px}.video-card:hover .save-card,.save-card:focus-visible,.save-card.saved{opacity:1}.video-card h3{font-size:15px;line-height:1.38;font-weight:600;margin:11px 0 5px;display:-webkit-box;-webkit-box-orient:vertical;-webkit-line-clamp:2;overflow:hidden}.video-card h3 a:hover{color:var(--accent)}.channel,.video-meta{font-size:13px;line-height:1.6;color:var(--muted);white-space:nowrap;overflow:hidden;text-overflow:ellipsis}.material-tags{display:flex;flex-wrap:wrap;gap:5px;margin-top:9px;min-height:25px;align-items:center}.material-tag{font-size:11px;line-height:1.5;display:inline-flex;align-items:center;gap:4px;color:var(--accent);background:var(--accent-soft);border-radius:5px;padding:3px 6px;white-space:nowrap}.material-tag svg{width:12px;height:12px}.material-tag:hover{filter:brightness(.95)}.material-missing{color:var(--muted);font-size:11px;display:flex;gap:5px;align-items:center}.material-missing svg{width:13px;height:13px}.load-row{text-align:center;margin:40px 0 0}.secondary{border:1px solid var(--line);background:var(--bg)}.load-row button{padding:11px 28px;border-radius:24px}.empty-state{grid-column:1/-1;max-width:520px;padding:65px 0;margin:auto;text-align:center}.empty-state svg{width:38px;height:38px;margin:0 auto 16px;color:var(--muted)}.empty-state h2{font-size:22px;margin-bottom:8px}.empty-state p{color:var(--muted);margin-bottom:18px}.primary{display:inline-flex;align-items:center;justify-content:center;gap:8px;background:var(--ink);color:var(--bg);border-radius:8px;padding:10px 16px;font-weight:600}.primary:hover{opacity:.86}
.watch-back{display:inline-flex;align-items:center;gap:7px;font-size:13px;color:var(--muted);margin:1px 0 17px}.watch-back svg{width:16px;height:16px}.watch-layout{display:grid;grid-template-columns:minmax(0,1fr) 300px;gap:26px}.player{aspect-ratio:16/9;background:#090909;position:relative;border-radius:12px;overflow:hidden}.player-poster{width:100%;height:100%;object-fit:contain;opacity:.8}.player button{position:absolute;inset:0;display:flex;align-items:center;justify-content:center;width:100%;height:100%;background:transparent}.play-icon{display:grid;place-items:center;border-radius:16px;background:#000c;color:#fff;width:76px;height:53px}.play-icon svg{width:28px;height:28px;fill:currentColor}.player iframe{width:100%;height:100%;border:0}.watch-title{font-size:23px;line-height:1.35;margin:17px 0 10px;font-weight:650}.watch-meta{display:flex;align-items:center;justify-content:space-between;gap:15px;margin-bottom:18px}.watch-channel{font-weight:600;font-size:14px}.watch-meta .video-meta{white-space:normal}.actions{display:flex;flex-wrap:wrap;gap:9px;align-items:center}.actions button,.actions a.button{font-size:13px}.watch-actions{display:flex;gap:8px;flex-shrink:0}.watch-actions button,.watch-actions a{display:inline-flex;gap:7px;align-items:center;padding:9px 12px;background:var(--soft);border-radius:20px;font-size:12px}.watch-actions svg{width:17px;height:17px}.description{background:var(--soft);padding:16px;border-radius:12px;font-size:14px;line-height:1.65;margin-bottom:24px}.description p{max-width:75ch}.description details{margin-top:9px}.description summary{cursor:pointer;font-weight:600;font-size:12px}.description details p{margin-top:8px;color:var(--muted)}.resource-heading{display:flex;align-items:center;justify-content:space-between;gap:12px;margin:25px 0 14px}.resource-heading h2{font-size:20px}.ready-label{font-size:12px;color:var(--green);display:inline-flex;align-items:center;gap:5px}.ready-label svg{width:14px;height:14px}.resource-summary{display:flex;gap:8px;flex-wrap:wrap}.resource-summary a{display:flex;gap:7px;align-items:center;font-size:12px;border:1px solid var(--line);padding:9px;border-radius:6px}.resource-summary svg{width:16px;height:16px;color:var(--accent)}.resource-summary a:hover{background:var(--soft)}.tabs{display:flex;gap:3px;overflow-x:auto;border-bottom:1px solid var(--line);margin:24px 0}.tabs button{white-space:nowrap;background:transparent;border-radius:0;font-size:13px;padding:12px 11px;color:var(--muted);border-bottom:2px solid transparent}.tabs button[aria-selected=true]{border-color:var(--ink);color:var(--ink)}.study-panel{padding:2px 0 20px;min-width:0}.study-panel h2{font-size:21px;line-height:1.4;margin-bottom:12px}.study-panel h3{font-size:16px;margin:23px 0 7px}.study-panel p{margin:0 0 14px;line-height:1.7}.study-panel li{margin:7px 0}.study-panel ul,.study-panel ol{padding-left:22px}.reading{max-width:75ch}.reading section{margin:20px 0}.source{font-size:12px;color:var(--accent);white-space:nowrap;text-decoration:underline;text-underline-offset:3px}.example{background:var(--soft);padding:1px 18px 12px;border-radius:10px}.no-materials{border-top:1px solid var(--line);padding:22px 0;margin-top:24px}.no-materials h2{font-size:20px}.no-materials p{color:var(--muted);margin:9px 0 15px}.unavailable-types{display:flex;flex-wrap:wrap;gap:9px;margin:16px 0}.unavailable-types span{font-size:12px;display:flex;gap:6px;align-items:center;color:var(--muted);background:var(--soft);padding:7px 10px;border-radius:6px}.unavailable-types svg{width:14px;height:14px}.text-link{font-weight:600;color:var(--accent);text-decoration:underline;text-underline-offset:3px}.related-list h2{font-size:15px;margin-bottom:14px}.related-item{display:grid;grid-template-columns:128px minmax(0,1fr);gap:10px;margin-bottom:17px}.related-item .thumbnail{border-radius:8px}.related-item h3{font-size:12px;line-height:1.4;font-weight:600;display:-webkit-box;-webkit-box-orient:vertical;-webkit-line-clamp:3;overflow:hidden}.related-item p{font-size:11px;color:var(--muted);margin-top:5px}.related-item .duration{font-size:10px;line-height:14px}
.quiz-item{border:0;border-bottom:1px solid var(--line);padding:0 0 20px;margin:0 0 24px}.quiz-item legend{font-weight:600;margin-bottom:12px;line-height:1.5}.option{display:flex;gap:11px;align-items:flex-start;padding:10px 12px;background:var(--soft);border:1px solid transparent;margin-bottom:7px;border-radius:6px;cursor:pointer}.option:has(input:checked){border-color:var(--ink)}input[type=radio]{margin-top:5px;accent-color:var(--accent)}.explanation,.status{background:var(--tint);padding:14px;margin-top:12px;border-radius:8px}.explanation.wrong{background:var(--accent-soft)}.status{margin:0 0 18px}.flashcard{border:1px solid var(--line);border-radius:12px;padding:36px 24px;min-height:250px;display:flex;flex-direction:column;justify-content:center;align-items:center;text-align:center;margin:20px 0}.flashcard .prompt{font-size:24px;line-height:1.4}.flashcard .answer{font-size:18px}.card-face-label{font-size:11px;color:var(--muted);margin-bottom:13px}.flash-meta{display:flex;justify-content:space-between;gap:12px;font-size:12px;color:var(--muted)}.editor{margin:20px 0;padding:18px;background:var(--soft);border-radius:8px}.editor textarea{display:block;width:100%;min-height:90px;padding:10px;margin:6px 0 15px;border:1px solid var(--line);border-radius:6px;background:var(--bg);color:var(--ink)}.outline{display:grid;grid-template-columns:1fr 1fr;gap:17px}.outline article{border:1px solid var(--line);border-radius:10px;padding:18px}.outline article h3{margin-top:5px}.download-grid{display:grid;grid-template-columns:1fr 1fr;gap:12px}.download-grid a{border:1px solid var(--line);border-radius:9px;padding:17px}.download-grid a:hover{background:var(--soft)}.download-grid strong{display:block;font-size:13px;margin-bottom:5px}.download-grid span{color:var(--muted);font-size:12px}.small{font-size:12px}.muted{color:var(--muted)}.spacer{height:20px}.page-heading{font-size:27px;margin:5px 0 10px}.page-lede{font-size:14px;color:var(--muted);margin-bottom:25px}.guide{max-width:760px}.guide section{margin:30px 0}.guide h2{font-size:20px;margin-bottom:10px}.guide p,.guide li{line-height:1.8;margin:9px 0}.guide a{color:var(--accent);text-decoration:underline;text-underline-offset:3px}.toast,#storage-warning{position:fixed;bottom:22px;left:50%;transform:translateX(-50%);background:var(--ink);color:var(--bg);padding:12px 20px;border-radius:9px;box-shadow:0 7px 22px #0002;z-index:30;font-size:13px;max-width:calc(100% - 30px)}#storage-warning{bottom:70px}.nav-scrim{position:fixed;inset:64px 0 0;background:#0006;border-radius:0;z-index:8}
@media(min-width:1650px){.video-grid{grid-template-columns:repeat(4,minmax(0,1fr))}.watch-layout{grid-template-columns:minmax(0,1fr) 360px}.related-item{grid-template-columns:155px minmax(0,1fr)}}
@media(max-width:1150px){:root{--sidebar:200px}.brand-group{width:168px;gap:12px}.topbar{gap:25px}.sidebar{padding-left:8px;padding-right:8px}.nav-link{gap:15px;padding-left:12px}main{padding-left:20px;padding-right:20px}.video-grid{grid-template-columns:repeat(2,minmax(0,1fr))}.watch-layout{grid-template-columns:minmax(0,1fr)}.related-list{display:grid;grid-template-columns:1fr 1fr;gap:12px 20px}.related-list h2{grid-column:1/-1}.filters{grid-template-columns:1fr 1fr}}
@media(max-width:850px){:root{--sidebar:0px}.sidebar{width:232px;visibility:hidden;transform:translateX(-100%);transition:transform 180ms cubic-bezier(.16,1,.3,1)}body.nav-open .sidebar{visibility:visible;transform:translateX(0)}body.nav-open .nav-scrim{display:block!important}.brand-group{width:auto;gap:10px}.topbar{gap:20px;padding-right:14px}.header-actions{gap:2px}.brand{font-size:20px}main{padding-top:78px}.watch-title{font-size:22px}}
@media(min-width:851px){body.nav-collapsed{--sidebar:0px}body.nav-collapsed .sidebar{transform:translateX(-100%)}}
@media(max-width:560px){.topbar{height:108px;padding:8px 12px 54px;gap:12px}.brand-group{margin-right:auto}.brand{font-size:21px}.search-form{position:absolute;top:60px;left:16px;width:calc(100% - 32px);height:36px;max-width:none}.search-form input{font-size:14px}.search-submit{width:50px}.sidebar{top:108px}.nav-scrim{top:108px}.icon-button{width:36px;height:36px}main{padding:120px 16px 38px}.topic-strip{margin-right:-16px;padding-right:16px}.topic-chip{padding:7px 11px;min-height:36px}.catalog-toolbar{margin-top:4px;margin-bottom:10px;gap:8px}.toolbar-left{gap:9px}.filter-button{padding:8px 10px}.filter-button svg{width:16px;height:16px}#result-count{font-size:11px}.sort-control{font-size:0;gap:0}.sort-control select{font-size:12px;max-width:125px}.material-filter-row{display:block;margin-bottom:21px}.filter-label{display:block;margin-bottom:7px;font-size:11px}.material-filters{margin-right:-16px;padding-right:16px}.material-filter{min-height:34px}.video-grid{grid-template-columns:1fr;gap:28px}.video-card h3{font-size:16px;margin-top:10px}.channel,.video-meta{font-size:13px}.save-card{opacity:1}.material-tag{font-size:11px;padding:4px 7px}.material-tags{gap:6px}.material-missing{font-size:12px}.filters{grid-template-columns:1fr 1fr;padding:14px;gap:12px}.filters label:first-child{grid-column:1/-1}.watch-layout{gap:28px}.watch-title{font-size:21px}.watch-meta{align-items:flex-start;flex-direction:column}.watch-actions{width:100%}.watch-actions button,.watch-actions a{min-height:40px}.resource-heading h2{font-size:19px}.tabs{margin-right:-16px}.tabs button{min-height:44px}.outline,.download-grid{grid-template-columns:1fr}.flashcard{padding:28px 18px}.flashcard .prompt{font-size:21px}.flash-meta{flex-wrap:wrap}.study-panel .actions button{min-height:42px}.related-list{display:block}.related-item{grid-template-columns:145px minmax(0,1fr)}.page-heading{font-size:25px}}
@media(prefers-reduced-motion:reduce){*{transition:none!important;scroll-behavior:auto!important}}
.text-button:hover{background:var(--accent-soft);color:var(--accent)}
/* The sidebar has one scrolling category region and a pinned personal library. */
#main-nav{flex:0 0 auto}.sidebar-categories{display:flex;flex-direction:column;flex:1 1 auto;min-height:0;margin-top:9px;overflow:hidden}.category-heading{display:flex;align-items:center;justify-content:space-between;gap:8px;flex:0 0 auto;padding:12px 10px 9px;border-top:1px solid var(--line)}.category-heading h2{font-size:13px;font-weight:600}.category-heading h2 a:hover{color:var(--accent)}.category-heading>span{font-size:10px;color:var(--muted);white-space:nowrap}.category-scroll{flex:1 1 auto;min-height:0;overflow-y:auto;overscroll-behavior:contain;scrollbar-gutter:stable}.category-link{display:flex;align-items:center;gap:8px;padding:9px 9px 9px 10px;border-radius:8px;font-size:12px;line-height:1.4;min-height:38px}.category-link:hover,.category-link.active{background:var(--soft)}.category-link.active{font-weight:600;color:var(--accent)}.category-name{flex:1;min-width:0;overflow-wrap:anywhere}.category-score{flex:0 0 auto;min-width:33px;text-align:right;font-size:11px;color:var(--muted);font-variant-numeric:tabular-nums}.category-more{flex:0 0 auto;display:flex;align-items:center;justify-content:center;gap:7px;width:100%;padding:9px 8px;margin:6px 0;font-size:12px;background:transparent;min-height:36px}.category-more svg{width:16px;height:16px}.sidebar-footer{flex:0 0 auto;border-top:1px solid var(--line);background:var(--bg);padding:7px 0 max(6px,env(safe-area-inset-bottom))}.sidebar-footer .nav-section-label{padding:7px 14px 5px}.sidebar-footer .sidebar-bottom{margin:0;padding:10px 14px 3px;font-size:11px}.category-ranking-header{display:flex;justify-content:space-between;gap:20px;max-width:900px;padding:12px 14px;color:var(--muted);font-size:12px;border-bottom:1px solid var(--line)}.category-ranking{list-style:none;padding:0;margin:0 0 20px;max-width:900px}.category-ranking li a{display:flex;align-items:center;gap:16px;padding:14px;border-bottom:1px solid var(--line)}.category-ranking li a:hover{background:var(--soft)}.category-rank{min-width:24px;color:var(--muted);font-size:12px;font-variant-numeric:tabular-nums}.ranked-category-name{flex:1;min-width:0;font-size:14px;font-weight:600;overflow-wrap:anywhere}.ranked-category-name small{display:block;color:var(--muted);font-weight:400;font-size:12px;margin-top:4px}.ranked-category-score{font-variant-numeric:tabular-nums;font-weight:600;font-size:14px}.category-page-more{display:flex;align-items:center;gap:7px}.category-page-more svg{width:16px;height:16px}
@media(max-height:650px){#main-nav .nav-link{padding-top:8px;padding-bottom:8px}#main-nav .nav-divider{margin:6px 0}.sidebar-categories{margin-top:4px}.category-heading{padding-top:8px;padding-bottom:7px}.sidebar-footer{padding-top:3px}.sidebar-footer .nav-link{padding-top:7px;padding-bottom:7px}.sidebar-footer .nav-section-label{padding-top:4px;padding-bottom:4px}.sidebar-footer .sidebar-bottom{padding-top:6px}.category-more{margin:3px 0;padding:6px}}
@media(max-height:420px){#main-nav{display:flex;justify-content:space-between}#main-nav .nav-divider{display:none}#main-nav .nav-link{justify-content:center;padding:7px 14px;gap:0}#main-nav .nav-link>span{display:none}.sidebar-footer #library-nav{display:grid;grid-template-columns:1fr 1fr}.sidebar-footer .nav-section-label{grid-column:1/-1}.sidebar-footer .nav-link{font-size:11px;padding:6px;gap:6px}.sidebar-footer .nav-link svg{width:16px;height:16px}.sidebar-footer .nav-count{display:none}.sidebar-footer .sidebar-bottom{padding-top:4px}.category-heading{padding-top:6px}.category-more{min-height:30px}}
@media(max-width:560px){.category-link{min-height:44px}.category-more{min-height:40px}.category-ranking li a{gap:9px;padding:12px 6px}.category-ranking-header{padding-left:6px;padding-right:6px}.ranked-category-name small{font-size:11px}}
/* Purchase and fulfillment use the existing video-library typography and colors. */
.purchase-panel{border-top:1px solid var(--line);padding:24px 0;margin-top:20px;max-width:760px}.purchase-intro{color:var(--muted);max-width:620px;margin:10px 0 18px;font-size:14px;line-height:1.7}.delivery-label{font-size:12px;color:var(--accent);font-weight:600}.purchase-includes{list-style:none;display:flex;flex-wrap:wrap;gap:12px 22px;padding:0;margin:16px 0 24px;font-size:13px}.purchase-includes li{display:flex;align-items:center;gap:7px}.purchase-includes svg{width:17px;height:17px;color:var(--muted)}#purchase-form label,.recover-form label{display:block;font-size:13px;font-weight:600;margin:0 0 8px}#purchase-form input,.recover-form input{display:block;width:min(100%,390px);height:44px;padding:10px 12px;border:1px solid var(--line);border-radius:8px;background:var(--bg);color:var(--ink);font:inherit}.purchase-action{display:flex;align-items:center;gap:14px;flex-wrap:wrap;margin-top:14px}.purchase-action>span{font-size:12px;color:var(--muted)}.purchase-terms{font-size:11px;color:var(--muted);margin-top:14px}.purchase-terms a{text-decoration:underline;text-underline-offset:3px}.form-message{font-size:13px;line-height:1.6;margin-top:10px;color:var(--accent)}.form-message:empty{display:none}.purchase-recover{border-top:1px solid var(--line);margin-top:22px;padding-top:16px;font-size:13px}.purchase-recover summary{cursor:pointer;color:var(--muted)}.recover-form{margin-top:15px}.recover-form input{margin:8px 0 12px}.commerce-loading{color:var(--muted);font-size:13px;padding:24px 0}.order-card{max-width:850px;margin:8px auto 0;padding:24px 14px 70px}.order-card .watch-back{margin-bottom:34px}.order-eyebrow{font-size:11px;font-weight:600;letter-spacing:.08em;color:var(--accent);margin-bottom:10px}.order-card h1{font-size:32px;line-height:1.2;letter-spacing:-.6px;margin-bottom:14px}.order-description{color:var(--muted);font-size:15px;line-height:1.7;max-width:680px}.order-video{display:flex;align-items:center;gap:18px;border-block:1px solid var(--line);padding:20px 0;margin:28px 0}.order-video img{width:150px;aspect-ratio:16/9;object-fit:cover;border-radius:8px}.order-video h2{font-size:15px;line-height:1.5}.order-video p{font-size:13px;color:var(--muted);margin-top:5px}.order-steps{display:flex;gap:24px;justify-content:space-between;list-style:none;padding:0;margin:27px 0 32px}.order-steps li{display:flex;align-items:center;gap:8px;font-size:12px;color:var(--muted)}.order-steps span{display:grid;place-items:center;width:25px;height:25px;border-radius:50%;background:var(--soft);flex:0 0 auto}.order-steps .current{font-weight:600;color:var(--ink)}.order-steps .current span{background:var(--ink);color:var(--bg)}.order-steps .complete span{color:var(--accent);background:var(--accent-soft)}.order-actions{display:flex;gap:12px;align-items:center;flex-wrap:wrap}.order-actions svg{width:18px;height:18px}.order-file-list{display:flex;flex-wrap:wrap;gap:12px 22px;padding:24px 0;border-bottom:1px solid var(--line)}.order-file-list button{display:flex;align-items:center;gap:7px;font-size:13px}.order-file-list svg{width:14px;height:14px}.notification-state,.order-support{color:var(--muted);font-size:12px;margin-top:18px}.order-reference{font-size:11px;color:var(--muted);margin-top:28px;overflow-wrap:anywhere}.order-reference summary{cursor:pointer}.order-reference p{margin:10px 0}.email-preview{font:13px/1.6 monospace;white-space:pre-wrap;overflow-wrap:anywhere;background:var(--soft);padding:20px;margin-top:22px;border-radius:8px}.download-item{text-align:left;display:flex;gap:12px;align-items:center}.download-item>svg{width:22px;height:22px}.download-item small{display:block;margin-top:4px;color:var(--muted)}button:disabled{opacity:.55;cursor:not-allowed}.purchase-action .primary,.order-actions .primary{display:inline-flex;align-items:center;justify-content:center;gap:8px}
@media(max-width:560px){.purchase-panel{padding-top:20px}.resource-heading{flex-wrap:wrap;gap:9px}.purchase-includes{gap:11px 18px}.purchase-action{align-items:stretch;flex-direction:column}.purchase-action .primary{width:100%;min-height:46px}#purchase-form input,.recover-form input{width:100%}.order-card{padding:8px 0 40px}.order-card h1{font-size:27px}.order-card .watch-back{margin-bottom:24px}.order-video{gap:12px}.order-video img{width:98px}.order-video h2{font-size:13px}.order-video p{font-size:11px}.order-steps{gap:10px;align-items:flex-start}.order-steps li{flex:1;flex-direction:column;align-items:flex-start;gap:8px;line-height:1.5}.order-actions>.primary{width:100%;min-height:46px}.order-file-list{gap:15px}.order-file-list button{min-height:32px}}
.purchase-panel .primary:hover,.order-actions .primary:hover{background:var(--ink);color:var(--bg)}.order-actions a.secondary{display:inline-flex;align-items:center;justify-content:center;padding:10px 16px;border-radius:8px;font-weight:600}.order-actions a.secondary:hover{background:var(--soft)}

/* Keep material access and reading tools in the player column. */
#watch-view{container-type:inline-size}.watch-layout{grid-template-columns:minmax(0,1fr);gap:16px 24px;align-items:start}.watch-video,.watch-info,#materials-access,#learning{min-width:0}.watch-title{margin-bottom:0}#materials-access,#learning{scroll-margin-top:125px}#materials-access .purchase-panel{border:0;padding:0;margin:0;max-width:none}#materials-access .resource-heading{margin:0 0 12px;flex-wrap:wrap;gap:6px 12px}#materials-access .resource-heading h2{font-size:19px}#materials-access .purchase-intro{margin:0 0 16px;font-size:16px;line-height:1.5;color:var(--ink)}#materials-access .purchase-intro>span{display:block}#materials-access .purchase-intro>span+span{margin-top:6px}#materials-access .material-inline{display:inline-block;font-weight:700;text-decoration:underline;text-underline-offset:3px;text-decoration-thickness:1px;border-radius:2px;cursor:pointer}#materials-access .purchase-delivery .material-inline,#materials-access .material-inline:hover{color:var(--accent)}#materials-access .purchase-action{gap:8px;margin-top:12px}#materials-access .primary{display:inline-flex;align-items:center;justify-content:center;gap:8px;width:100%;min-height:44px;padding:10px 12px;border-radius:8px;font-size:15px;font-weight:600}#materials-access .primary svg{width:18px;height:18px}#materials-access .purchase-action>span{width:100%}#materials-access .purchase-includes{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:10px 12px;margin:20px 0;font-size:12px}#materials-access .purchase-includes li{align-items:flex-start}#materials-access .purchase-includes svg{flex:0 0 auto;width:16px;height:16px}#materials-access .purchase-includes li:last-child{grid-column:1/-1}#materials-access .purchase-recover{margin-top:16px;padding-top:14px}#materials-access .resource-summary{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));margin-top:16px}#materials-access .resource-summary a{min-height:44px}.watch-info .description{margin-bottom:0}.watch-layout>.related-list{margin-top:8px}#learning .tabs{margin-top:8px}
@container(min-width:720px){.watch-layout{grid-template-columns:minmax(0,1fr) 300px}.watch-main{grid-column:1}.watch-layout>.related-list{grid-column:2;grid-row:1;display:block}.watch-layout .related-item{grid-template-columns:128px minmax(0,1fr)}}
@container(min-width:1180px){.watch-layout{grid-template-columns:minmax(0,1fr) 360px}.watch-layout .related-item{grid-template-columns:155px minmax(0,1fr)}}
@media(max-width:560px){#materials-access .primary{min-height:46px}#materials-access .purchase-includes{margin:16px 0}#materials-access .purchase-recover{margin-top:12px;padding-top:12px}}

/* Guest access keeps the player mounted and reveals checkout only on intent. */
#materials-access .resource-summary a{font-size:14px;font-weight:600;transition:background-color 120ms,border-color 120ms}#materials-access .resource-summary a:hover{background:var(--accent-soft);border-color:var(--accent);color:var(--accent)}#materials-access .resource-summary a:active{background:var(--soft)}#materials-access [aria-disabled=true]{cursor:wait;opacity:.6}#materials-access .material-formats{font-size:12px;color:var(--muted);margin-top:10px}#materials-access .access-feedback:empty{display:none}#materials-access .access-feedback{margin-top:14px;font-size:14px;line-height:1.5}#materials-access .access-feedback p{margin:0 0 10px}#materials-access .access-feedback h3{font-size:16px;margin:0 0 6px}#materials-access .access-feedback .secondary{display:inline-flex;align-items:center;min-height:44px;padding:9px 12px;border-radius:8px}#purchase-details{margin-top:16px;padding-top:16px;border-top:1px solid var(--line)}#purchase-details .checkout-summary{font-size:14px;line-height:1.5;margin:0 0 14px}#materials-access #purchase-email{font-size:16px}#materials-access .resource-summary a:focus-visible{outline:2px solid var(--accent);outline-offset:3px}
/* A brief focus cue points to the delivery email without moving the layout. */
@keyframes email-focus-nudge{0%,100%{transform:translateX(0)}20%{transform:translateX(-4px)}40%{transform:translateX(4px)}60%{transform:translateX(-3px)}80%{transform:translateX(2px)}}
#materials-access #purchase-email:focus{animation:email-focus-nudge 360ms ease-in-out 1}
@media(prefers-reduced-motion:reduce){#materials-access #purchase-email:focus{animation:none}}

/* Language switching updates UI text in place, preserving playback and drafts. */
.language-toggle{flex:0 0 auto;min-width:40px;min-height:36px;padding:6px 8px;border:1px solid var(--line);border-radius:7px;background:var(--bg);color:var(--ink);font-size:13px;font-weight:600;white-space:nowrap}.language-toggle:hover{background:var(--soft)}html[lang="zh-CN"] body{font-family:Arial,"PingFang SC","Microsoft YaHei",sans-serif}html[lang="zh-CN"] .category-heading>span{font-size:10px}@media(max-width:360px){.topbar{gap:4px}.brand-group{gap:4px}.brand{font-size:19px}.header-actions{gap:0}.header-actions .icon-button{width:32px}.language-toggle{min-width:36px;padding:6px}}

/* Public video context and HN discussions share the existing reading column. */
.watch-reading{min-width:0}.watch-reading #learning:not(.hidden){margin-bottom:32px}.video-overview{border-top:1px solid var(--line);padding-top:20px;margin-top:20px}.video-overview h2,.comments-heading h2{font-size:20px;line-height:1.4;margin:0}.overview-summary{font-size:16px;line-height:1.65;margin:12px 0;max-width:75ch;overflow-wrap:anywhere}.overview-facts{display:flex;flex-wrap:wrap;gap:8px 14px;font-size:13px;line-height:1.6;margin:16px 0}.overview-facts>span{color:var(--muted)}.overview-facts a{color:var(--accent);text-decoration:underline;text-underline-offset:3px}.video-overview h3{font-size:16px;line-height:1.5;margin:24px 0 8px}.overview-context{font-size:15px;line-height:1.7;max-width:75ch;overflow-wrap:anywhere}.overview-comments-link{min-height:44px;padding:10px 0;text-decoration:underline;text-underline-offset:3px}.hn-comments{scroll-margin-top:128px}.comments-heading{display:flex;align-items:baseline;flex-wrap:wrap;gap:8px 16px}.comments-count,.comments-order,.comments-progress{font-size:13px;line-height:1.6;color:var(--muted)}.comments-order{margin:8px 0 0}.comments-status{margin:16px 0;font-size:15px;line-height:1.6}.hn-comment{padding:22px 0;border-bottom:1px solid var(--line);overflow-wrap:anywhere;scroll-margin-top:128px}.hn-comment-meta{display:flex;align-items:baseline;flex-wrap:wrap;gap:6px 12px;font-size:13px;line-height:1.6}.hn-comment-author{font-weight:700;color:var(--ink);text-decoration:underline;text-underline-offset:3px}.hn-comment-meta time{color:var(--muted)}.hn-stance{background:var(--soft);padding:2px 7px;border-radius:5px;font-size:12px}.hn-thread-title{font-size:13px;line-height:1.6;color:var(--muted);margin:10px 0}.hn-thread-title a:hover{color:var(--accent);text-decoration:underline}.hn-comment-text{font-size:15px;line-height:1.7;white-space:pre-line;max-width:75ch;margin:12px 0 4px}.hn-comment-actions{display:flex;align-items:center;flex-wrap:wrap;gap:4px 18px}.hn-comment-actions a,.hn-comment-actions button{display:inline-flex;align-items:center;min-height:44px;padding:10px 0;font-size:13px;line-height:1.5;color:var(--accent);text-decoration:underline;text-underline-offset:3px}.hn-comment-actions a:hover,.overview-comments-link:hover{color:var(--ink)}.comments-pagination{display:flex;align-items:center;justify-content:space-between;flex-wrap:wrap;gap:12px;margin-top:20px}.comments-pagination button,.comments-content>[data-retry-comments]{min-height:44px}.hn-comments:focus-visible,.hn-comment:focus-visible{outline:2px solid var(--accent);outline-offset:4px}[data-comment-preview][hidden],[data-comment-full][hidden],[data-more-comments][hidden]{display:none!important}
/* A single reading column keeps study tools directly below the mounted player. */
.watch-main{min-width:0;container-type:inline-size;--player-top:76px;--player-height:min(56.25cqi,50vh)}.watch-main>.player{z-index:2;max-height:50vh}.watch-video{margin-bottom:20px}.watch-video .watch-title{margin-bottom:12px}.watch-video .watch-meta{margin-bottom:0}.watch-main>#materials-access{border-top:1px solid var(--line);padding-top:20px}.free-material-bar{display:flex;align-items:center;justify-content:space-between;flex-wrap:wrap;gap:12px 16px}.free-material-bar h2,.materials-pending h2{font-size:20px;line-height:1.4;margin:0 0 4px}.free-label{font-size:14px;font-weight:600;color:var(--accent)}#materials-access .free-material-bar .primary{width:auto}.free-material-intro,.materials-pending p{font-size:15px;line-height:1.6;margin:12px 0 8px}.materials-pending .text-link{display:inline-flex;align-items:center;min-height:44px;font-size:14px}.watch-main>#learning{margin-bottom:32px}#learning .tabs{margin:8px 0 20px;gap:4px;background:var(--bg);z-index:3;position:relative}.tabs button{min-height:44px}.tabs button:focus-visible{outline:2px solid var(--accent);outline-offset:-3px}.watch-reading .hn-comments{margin-top:28px}.watch-main #learning,.watch-main #tab-content{scroll-margin-top:calc(var(--player-top) + var(--player-height) + 60px)}
@media(min-height:620px){.watch-main>.player{position:sticky;top:var(--player-top)}#learning .tabs{position:sticky;top:calc(var(--player-top) + var(--player-height));padding-top:8px}}
@media(max-width:560px){.watch-main{--player-top:108px}.watch-video{margin-bottom:16px}.watch-video .watch-meta{gap:12px}.watch-main>#materials-access{padding-top:16px}.free-material-bar{align-items:flex-start}.free-material-bar h2,.materials-pending h2{font-size:19px}#materials-access .free-material-bar .primary{min-height:44px;font-size:14px}.free-material-intro{margin-bottom:4px}#learning .tabs{margin-right:0;padding-right:4px}.watch-main>.player{border-radius:8px}}

/* Public reading pages share the catalog's flat Arial and orange system. */
#seo-view{min-width:0;max-width:100%}.seo-breadcrumbs{display:flex;flex-wrap:wrap;gap:6px;font-size:12px;color:var(--muted);margin:0 0 20px}.seo-breadcrumbs a,.seo-start-links a,.seo-article a,.seo-pagination a,.watch-channel a,.channel a{color:var(--accent);text-decoration:underline;text-underline-offset:3px}.seo-article{max-width:75ch;margin:0}.seo-article h1,#catalog-view>h1{font-size:28px;line-height:1.25;font-weight:650;letter-spacing:-.02em;margin:0 0 14px;text-wrap:balance}.seo-article h2{font-size:21px;line-height:1.35;margin:30px 0 12px}.seo-article h3{font-size:17px;margin:24px 0 8px}.seo-article p,.seo-article li{line-height:1.75;overflow-wrap:anywhere}.seo-article ul,.seo-article ol{padding-left:22px}.seo-article li{margin:7px 0}.seo-start-links{font-size:13px;line-height:1.8;margin:14px 0 25px}.seo-table{overflow-x:auto;max-width:100%;margin:20px 0}.seo-table table{width:100%;border-collapse:collapse;font-size:14px;line-height:1.6}.seo-table th,.seo-table td{padding:10px 12px;text-align:left;vertical-align:top;border-bottom:1px solid var(--line);min-width:125px}.seo-table th{font-weight:600;background:var(--soft)}.seo-pagination{display:flex;flex-wrap:wrap;justify-content:space-between;align-items:center;gap:16px;border-top:1px solid var(--line);padding-top:20px;margin:28px 0;font-size:13px}.seo-pagination a{padding:8px 0}.before-watch{border-top:1px solid var(--line);margin-top:25px;padding-top:22px;max-width:75ch}.before-watch p{line-height:1.75;margin:10px 0}.before-watch h2{font-size:20px}.before-watch h3{font-size:16px;margin-top:22px}.before-watch a{color:var(--accent);text-decoration:underline;text-underline-offset:3px}#catalog-view>p{max-width:75ch;color:var(--muted);font-size:14px;line-height:1.7;margin-bottom:12px}::selection{background:var(--accent-soft);color:var(--ink)}input,textarea{caret-color:var(--accent)}
@media(max-width:400px){.seo-article h1,#catalog-view>h1{font-size:24px}.seo-article h2{font-size:20px}.seo-table th,.seo-table td{padding:8px;min-width:112px}.seo-pagination{gap:10px}.watch-title{font-size:21px}.watch-main{min-width:0}.watch-actions{flex-wrap:wrap}}

.catalog-heading{font-size:18px;line-height:1.4;margin:0 0 16px}