/* Three chapters: particle opening, molecule and classroom, then photos and entry. */
.second-ui{min-height:0;padding:110px 5vw 72px}
.second-ui .reveal-heading{margin-bottom:32px}
.reveal-grid{grid-template-columns:minmax(0,1fr) minmax(0,1.08fr);gap:4vw;align-items:center}
.stage-slot{aspect-ratio:16/9;max-height:none}
.classroom-video-panel{min-width:0;padding:0}
.classroom-video-panel h3{font-size:clamp(26px,2.5vw,40px);line-height:1.3;font-weight:500;letter-spacing:-.035em;margin:14px 0}
.classroom-video-panel>p{color:#738e9f;font-size:13px;line-height:1.8;margin:0 0 28px}
.classroom-video-frame{position:relative;aspect-ratio:16/9;border:1px solid #d6e7f0;border-radius:22px;overflow:hidden;background:#dcecf5;box-shadow:0 20px 55px #49738b16}
.classroom-video-frame video{display:block;width:100%;height:100%;object-fit:contain}
.classroom-video-start{position:absolute;inset:0;border:0;color:white;cursor:pointer;background:linear-gradient(0deg,#173a5480,transparent 75%);display:flex;flex-direction:column;align-items:center;justify-content:center;gap:10px}
.classroom-video-start>span{display:grid;place-items:center;width:62px;height:62px;padding-left:4px;border:1px solid #ffffffa3;border-radius:50%;background:#f4fbff30;backdrop-filter:blur(8px);font-size:18px;transition:transform .2s}
.classroom-video-start:hover>span{transform:scale(1.07)}
.classroom-video-start strong{font-size:17px;font-weight:500;text-shadow:0 1px 10px #173a54}
.classroom-video-start small{font-size:11px;color:#e3f2fb}
.classroom-video-note{display:flex;justify-content:space-between;gap:18px;margin-top:15px;font-size:10px;color:#829baa}
.classroom-video-note a{color:#218bca;text-decoration:none}
.classroom-gallery{padding:95px 0 38px;min-height:100svh;background:radial-gradient(ellipse at 50% 44%,#e1f1fa 0%,#f0f8fc 72%);scroll-margin-top:0}
.classroom-heading{display:block;text-align:center;max-width:1200px}
.classroom-heading>div{display:block}
.classroom-heading h2{font-size:clamp(32px,3.5vw,50px);margin:12px 0}
.classroom-heading p{max-width:none;font-size:13px}
.classroom-stage{height:clamp(280px,32vw,460px);margin:24px auto 0;perspective:1500px;max-width:1800px}
.classroom-card{width:min(46vw,680px);height:calc(min(46vw,680px)*.625);padding:3px;border:1px solid #ffffff;border-radius:20px;background:#f6fbfe;box-shadow:0 22px 50px #416d8b24;transition:transform 1.1s cubic-bezier(.16,1,.3,1),opacity .65s,filter .8s}
.classroom-card img,.classroom-card.is-side img{object-fit:contain;border-radius:16px;background:#e8f2f7}
.classroom-card.is-side{filter:brightness(.88) saturate(.9);box-shadow:0 14px 30px #416d8b20}
.classroom-card.is-far{filter:brightness(.8) saturate(.85)}
.classroom-card:not(.is-side){box-shadow:0 24px 65px #416d8b30}
.classroom-caption{max-width:1100px;margin-top:14px}
.classroom-caption h3{font-size:16px}
.classroom-gallery .workspace-panel{position:relative;max-width:1180px;margin:32px auto 0;padding:22px 28px;border:1px solid #dceaf2;border-radius:24px;background:#ffffffed;box-shadow:0 16px 45px #38627c0d;display:grid;grid-template-columns:220px minmax(0,1fr);column-gap:26px;align-items:center}
.classroom-gallery .workspace-panel>.reveal-eyebrow{grid-column:1;grid-row:1;font-size:9px}
.classroom-gallery .workspace-panel h3{grid-column:1;grid-row:2;font-size:22px;margin:7px 0;line-height:1.3}
.classroom-gallery .workspace-panel>p{grid-column:1;grid-row:3;margin:0;font-size:10px;line-height:1.7}
.classroom-gallery .workspace-grid{grid-column:2;grid-row:1/4;display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:12px}
.classroom-gallery .workspace-grid a{min-height:92px;padding:14px 30px 14px 17px;border-radius:16px;animation:none!important;transform:none;box-sizing:border-box}
.classroom-gallery .workspace-grid a>span{position:static;width:auto;font-size:8px;letter-spacing:.6px}
.classroom-gallery .workspace-grid strong{font-size:18px;font-weight:550;margin:2px 0}
.classroom-gallery .workspace-grid small{font-size:9px;line-height:1.5;padding:0}
.classroom-gallery .workspace-grid i{font-size:20px;right:12px;bottom:16px}
.classroom-gallery .workspace-grid a:hover{transform:translateY(-3px);background:#e9f5fc;border-color:#9acfe9}
.classroom-gallery .workspace-note{display:none}
.classroom-foot{max-width:1180px;padding:0;margin-top:22px}
#workspace-title:focus{outline:none}
@media(max-width:1250px){.classroom-gallery .workspace-panel,.classroom-foot{margin-left:5vw;margin-right:5vw}.classroom-gallery .workspace-panel{grid-template-columns:190px minmax(0,1fr);gap:18px}.classroom-gallery .workspace-grid{gap:8px}.classroom-gallery .workspace-grid a{padding-left:12px}.classroom-gallery .workspace-grid small{max-width:140px}}
@media(max-width:900px){.second-ui{padding:105px 24px 48px}.reveal-grid{gap:24px}.classroom-video-panel h3{font-size:27px}.classroom-video-panel>p{margin-bottom:18px;font-size:12px}.classroom-gallery .workspace-panel{display:block;padding:22px}.classroom-gallery .workspace-grid{margin-top:18px}.classroom-stage{height:40vw}.classroom-card{width:57vw;height:calc(57vw*.625)}}
@media(max-width:700px){.reveal-grid{grid-template-columns:1fr}.stage-slot{aspect-ratio:16/9}.classroom-video-panel{margin-top:12px}.classroom-gallery{padding-top:85px}.classroom-heading{padding:0 20px}.classroom-heading h2{font-size:34px}.classroom-heading p{font-size:12px}.classroom-stage{height:62vw;margin-top:22px;perspective:950px}.classroom-card{width:82vw;height:calc(82vw*.625);padding:2px;border-radius:17px}.classroom-card img{border-radius:13px}.classroom-caption{gap:14px}.classroom-gallery .workspace-panel{margin-top:24px}.classroom-gallery .workspace-grid{grid-template-columns:1fr}.classroom-gallery .workspace-grid a{min-height:75px;display:grid;grid-template-columns:65px minmax(0,1fr);gap:2px 10px;padding:14px 32px 14px 16px}.classroom-gallery .workspace-grid a>span{grid-column:1;grid-row:1/3;align-self:center}.classroom-gallery .workspace-grid strong{grid-column:2;margin:0}.classroom-gallery .workspace-grid small{grid-column:2;max-width:none}.classroom-gallery .workspace-grid i{bottom:26px}.classroom-foot{flex-wrap:wrap;gap:12px;font-size:9px}.classroom-video-start>span{width:50px;height:50px}.second-ui .reveal-heading>p{font-size:12px}.classroom-caption h3{font-size:15px}}
@media(min-width:901px) and (max-height:850px){
  .classroom-gallery{padding-top:86px;padding-bottom:22px}
  .classroom-heading h2{font-size:36px;margin:9px 0}
  .classroom-heading p{font-size:12px}
  .classroom-stage{height:clamp(220px,calc(100svh - 470px),370px);margin-top:16px}
  .classroom-card{width:min(44vw,calc(max(210px,100svh - 485px)*1.6));height:calc(min(44vw,calc(max(210px,100svh - 485px)*1.6))*.625)}
  .classroom-caption{margin-top:9px}.classroom-caption h3{font-size:14px}.classroom-caption p{font-size:10px}
  .classroom-gallery .workspace-panel{margin-top:18px;padding:16px 22px;grid-template-columns:190px minmax(0,1fr)}
  .classroom-gallery .workspace-grid a{min-height:82px}.classroom-gallery .workspace-panel h3{font-size:20px}
  .classroom-foot{margin-top:16px}
}
@media(prefers-reduced-motion:reduce){.classroom-card,.classroom-video-start>span,.classroom-gallery .workspace-grid a{transition:none}}

/* Chapter navigation and classroom notes. */
.site-header nav a{padding:2px 0;transition:opacity .2s;border-bottom:1px solid transparent}
.site-header nav a.is-current{border-bottom-color:currentColor}
.hero-copy .message-button{width:230px;min-height:64px;justify-content:center;gap:30px;border:1px solid #d3e8f5;border-radius:12px;background:#edf7ff;color:#244c69;font-size:18px;font-weight:600;box-shadow:0 8px 30px #0c72b526;backdrop-filter:none}
.hero-copy .message-button svg{width:27px;height:27px;fill:#218eff;stroke:#218eff;stroke-width:.7;transition:transform .2s}
.hero-copy .message-button:hover{background:#fff}.hero-copy .message-button:hover svg{transform:translate(3px,-3px)}
.classroom-foot .motion-toggle{color:#51829a;border-color:#bdd7e7;background:#ffffffb3;flex-shrink:0}
.cover-message-dialog{position:fixed;z-index:1200;width:min(540px,calc(100vw - 32px));max-height:calc(100svh - 48px);padding:36px;border:1px solid #d4e7f2;border-radius:24px;background:#f3faff;color:#254b63;box-shadow:0 30px 100px #001e4059;overflow:auto;font-family:Geist,"Microsoft YaHei",sans-serif;color-scheme:light}
.cover-message-dialog::backdrop{background:#00152999;backdrop-filter:blur(8px)}
.cover-message-close{position:absolute;right:16px;top:14px;width:36px;height:36px;border:0;background:transparent;color:#598199;font-size:26px}
.cover-message-dialog h2{position:static;font-family:inherit;font-size:28px;line-height:1.35;letter-spacing:-.03em;margin:16px 0 12px}
.cover-message-note{font-size:12px;color:#7392a7;line-height:1.7;margin-bottom:26px}
.cover-message-dialog label{display:block;font-size:13px;margin:17px 0 8px}.cover-message-dialog label small{color:#87a0ae;font-size:11px;margin-left:6px}
.cover-message-dialog input,.cover-message-dialog textarea{display:block;width:100%;border:1px solid #d2e4ef;border-radius:12px;background:white;color:#244c69;padding:12px 14px;font:inherit;font-size:14px;line-height:1.7;resize:vertical}
.cover-message-dialog input:focus,.cover-message-dialog textarea:focus{outline:2px solid #9acfee;outline-offset:1px}.cover-message-dialog ::placeholder{color:#91a8b6}
.cover-message-submit{display:flex;align-items:center;justify-content:space-between;gap:14px;margin-top:18px}.cover-message-submit small{color:#87a0ae;font-size:11px}.cover-message-submit button{padding:12px 20px;border:0;border-radius:12px;background:#218eff;color:white;font-size:14px}
.cover-message-status{font-size:12px;line-height:1.7;color:#387c9f;min-height:20px;margin:14px 0 0}
.cover-message-history{border-top:1px solid #dbeaf3;margin-top:22px;padding-top:18px}.cover-message-history h3{font-size:13px;color:#7392a7;font-weight:500;margin:0 0 14px}.cover-message-history article{margin:14px 0}.cover-message-history strong{font-size:12px;font-weight:600}.cover-message-history p{font-size:13px;line-height:1.7;margin:5px 0;white-space:pre-wrap;overflow-wrap:anywhere}
body.cover-message-open{overflow:hidden}body.cover-message-open .custom-cursor{display:none}body.cover-message-open,body.cover-message-open *{cursor:auto}body.cover-message-open button{cursor:pointer}
@media(max-width:900px){.site-header nav{display:flex;left:auto;right:0;transform:none;gap:16px;padding:10px 16px}.site-header nav a{font-size:13px}}
@media(max-width:560px){.site-header{left:20px;right:20px}.brand{font-size:18px}.brand span{font-size:6px;letter-spacing:1.3px}.site-header nav{gap:12px;padding:10px 12px}.site-header nav a{font-size:12px}.hero-copy .message-button{width:190px;min-height:56px;font-size:17px}.cover-message-dialog{padding:28px 22px}.cover-message-dialog h2{font-size:25px}}

/* Tall model panel balances the whole title-and-video column, without scaling the molecule. */
@media(min-width:701px){.reveal-grid{grid-template-columns:minmax(0,.96fr) minmax(0,1.08fr);align-items:stretch;gap:5vw}.molecule-panel{display:flex;align-items:stretch}.stage-slot{aspect-ratio:auto;height:100%;min-height:0}.second-ui .reveal-heading{margin-bottom:30px}.second-ui{padding-bottom:48px}.classroom-video-panel>p{margin-bottom:23px}}
.classroom-gallery .workspace-panel{background:linear-gradient(120deg,#ffffff82,#e2f1f99e);border:1px solid #ffffffd9;box-shadow:0 20px 55px #355b7814,inset 0 1px #ffffff;backdrop-filter:blur(24px);max-width:1180px;padding:18px 24px;grid-template-columns:200px minmax(0,1fr)}
.classroom-gallery .workspace-grid{gap:14px}.classroom-gallery .workspace-grid a{position:relative;min-height:92px;padding:14px 38px 14px 17px;border:1px solid #ffffffed;box-shadow:0 10px 25px #47738e12,inset 0 1px #ffffff;overflow:hidden;background:linear-gradient(145deg,#ffffffab,#cde8f49c)}
.classroom-gallery .workspace-grid a:before{content:'';position:absolute;width:100px;height:100px;border-radius:50%;right:-35px;top:-35px;background:#9ad4ec42;filter:blur(8px)}
.classroom-gallery .workspace-grid .role-teach{background:linear-gradient(145deg,#ffffffba,#dfdef89c)}.classroom-gallery .workspace-grid .role-teach:before{background:#bcb8ef3b}.classroom-gallery .workspace-grid .role-manage{background:linear-gradient(145deg,#ffffffba,#e8efd29c)}.classroom-gallery .workspace-grid .role-manage:before{background:#c4d58a42}
.workspace-role-icon{position:absolute;right:15px;top:16px;width:23px;height:23px;color:#4c95b2}.role-teach .workspace-role-icon{color:#8880b4}.role-manage .workspace-role-icon{color:#8a9f46}
.classroom-gallery .workspace-grid a>span{font-size:8px;letter-spacing:1px;display:block;margin-bottom:6px}.classroom-gallery .workspace-grid strong{font-size:18px;margin:0 0 4px}.classroom-gallery .workspace-grid small{font-size:9px;line-height:1.5}.classroom-gallery .workspace-grid i{font-size:17px;bottom:17px}
.classroom-gallery .workspace-grid a:hover{transform:translateY(-4px);border-color:#b5d7ea;box-shadow:0 16px 30px #47738e22}.role-teach:hover{border-color:#c0bae2!important}.role-manage:hover{border-color:#c7d598!important}
@media(min-width:701px) and (max-width:1050px){.stage-slot{min-height:0}.classroom-gallery .workspace-panel{display:block}.classroom-gallery .workspace-grid{margin-top:18px}}
@media(max-width:700px){.classroom-gallery .workspace-panel{padding:18px}.classroom-gallery .workspace-grid a{display:block;min-height:85px;padding:13px 42px 13px 17px}.classroom-gallery .workspace-grid a>span{margin-bottom:8px}.classroom-gallery .workspace-grid strong{display:block}.classroom-gallery .workspace-grid i{bottom:20px}.workspace-role-icon{top:16px}.site-header nav{gap:13px}.site-header nav a{font-size:11px}.stage-slot{aspect-ratio:1.2;min-height:0}}

/* A tall structure visual beside the classroom title and complete video frame. */
.second-ui .molecule-panel{display:flex;flex-direction:column;align-items:stretch;min-width:0}
.classroom-video-copy{display:flex;flex-direction:column;justify-content:flex-start}
.second-ui .stage-slot{height:auto;aspect-ratio:1;min-height:0;max-height:calc(100svh - 260px);flex:none}
.second-ui .reveal-grid{grid-template-columns:minmax(0,1fr) minmax(0,1.12fr);align-items:stretch}
.second-ui .classroom-video-panel{display:flex;flex-direction:column;justify-content:center;gap:clamp(20px,2vw,32px)}
@media(max-width:700px){.second-ui .reveal-grid{grid-template-columns:1fr}.second-ui .classroom-video-panel{gap:18px}.second-ui .stage-slot{aspect-ratio:1.2;max-height:none}}

/* Anchor the gallery heading below the fixed chapter navigation. */
.classroom-gallery{padding-top:120px}
.classroom-gallery .workspace-panel{grid-template-columns:200px minmax(0,1fr);row-gap:0}
.classroom-gallery .workspace-grid{grid-row:1/3}
.classroom-gallery .workspace-grid strong{margin:8px 0 0}
@media(min-width:901px) and (max-height:1000px){
  .classroom-stage{height:clamp(220px,calc(100svh - 480px),460px)}
  .classroom-card{--classroom-preview-width:min(44vw,680px,calc(max(210px,100svh - 495px)*1.6));width:var(--classroom-preview-width);height:calc(var(--classroom-preview-width)*.625)}
}
@media(max-width:700px){.classroom-gallery{padding-top:110px}}