:root{font-family:Arial,Helvetica,sans-serif;font-size:18px;color:#233f50;background:#f8f6f0;--ink:#233f50;--muted:#687d87;--blue:#dcecf4;--accent:#456f86;--peach:#efd9c1;--line:#dce4e6;--cream:#faf6ec;color-scheme:light}*{box-sizing:border-box}body{margin:0}button,input{font:inherit;color:inherit}button,summary{cursor:pointer}button,a,input,summary{touch-action:manipulation}button{transition:background .16s,border-color .16s}button:disabled{opacity:.5;cursor:not-allowed}button:hover:not(:disabled){filter:brightness(.97)}button:focus-visible,a:focus-visible,summary:focus-visible,input:focus-visible{outline:3px solid #a27f56;outline-offset:3px}button{overflow-wrap:anywhere}a{color:inherit}img{max-width:100%}[hidden]{display:none!important}h1,h2,h3,p{overflow-wrap:break-word}h1,h2,h3{margin:0}h1,h2,.brand,.mode-switch button{font-family:Arial,Helvetica,sans-serif}h1{font-size:clamp(28px,3vw,40px);line-height:1.35;font-weight:700;letter-spacing:-.7px}h2{font-size:24px;line-height:1.5;font-weight:700}h3{font-size:21px;line-height:1.5;font-weight:800}.skip{position:fixed;left:15px;top:-100px;background:white;padding:15px;z-index:30}.skip:focus{top:15px}.header{min-height:100px;display:flex;align-items:center;gap:24px;padding:20px 4%;border-bottom:1px solid #e5dece;background:#fdfbf6}.brand{display:flex;align-items:center;gap:13px;text-decoration:none;font-size:22px;font-weight:700;line-height:1.4;flex-shrink:0}.brand small{display:block;letter-spacing:2px;font-family:Arial,Helvetica,sans-serif;font-size:13px;margin-top:4px;color:var(--muted)}.brand-mark{background:var(--blue);border:1px solid #c8dce5;border-radius:16px;display:grid;place-items:center;font-family:Arial,Helvetica,sans-serif;width:47px;height:47px;font-size:34px;padding-bottom:8px;color:var(--accent)}.header-note{font-family:Arial,Helvetica,sans-serif;font-style:normal;font-size:22px;color:#7093a6;margin-left:auto}.demo{background:#f1e7d7;border:1px solid #e5d5bf;padding:7px 14px;border-radius:18px;font-size:15px;white-space:nowrap}.layout{max-width:1640px;margin:auto;display:grid;grid-template-columns:260px minmax(0,1fr)}.sidebar{background:#fcfaf5;border-right:1px solid #e4dfd3;padding:30px 20px;min-width:0}.side-caption,.mini-label,.eyebrow{font-size:13px;font-weight:800;letter-spacing:1.7px;color:#9b7c59}.line-card{display:flex;gap:13px;align-items:center;margin:22px 0}.line-number{display:grid;place-items:center;flex-shrink:0;width:48px;height:54px;background:var(--blue);border:1px solid #cbdfe8;border-radius:15px;font-size:26px;font-weight:800;color:var(--accent)}.line-card strong{font-size:18px;display:block;margin-bottom:5px}.line-card div>span{display:block;font-size:16px;line-height:1.5;color:var(--muted)}#topics{display:grid;gap:6px}.topic-button{display:grid;grid-template-columns:23px minmax(0,1fr);gap:8px;align-items:start;text-align:left;width:100%;background:transparent;border:1px solid transparent;border-radius:15px;padding:12px 10px;font-size:16px;line-height:1.5}.topic-button.active{background:#e3eff4;border-color:#cfdee5;color:#244f66;font-weight:800}.topic-button:hover{background:#ecf2f4}.topic-number{font-size:14px;color:#8399a4;line-height:21px}.topic-button small{display:block;font-size:14px;color:var(--muted);font-weight:400;margin-top:5px}.sidebar-foot{margin:28px 8px 0;padding-top:25px;border-top:1px solid #e4dfd3}.sidebar-foot p{font-size:22px;font-family:Arial,Helvetica,sans-serif;font-style:normal;line-height:1.6;color:#648398}.sidebar-foot>span:last-child{font-size:15px;color:var(--muted)}main{min-width:0;padding:28px 38px 0;background-image:linear-gradient(#88a9bb0b 1px,transparent 1px),linear-gradient(90deg,#88a9bb0b 1px,transparent 1px);background-size:24px 24px}.breadcrumbs{font-size:15px;color:var(--muted)}.breadcrumbs span{margin:0 12px;color:#b8ab94}.page-heading{display:flex;align-items:center;justify-content:space-between;gap:24px;margin:23px 0 27px;padding:24px 27px;background:linear-gradient(115deg,#deedf4e8,#ebf3f6a8);border:1px solid #d7e6eb;border-radius:24px;position:relative}.page-heading>div{min-width:0}.page-heading .eyebrow{display:block;color:#648797;margin-bottom:9px}.page-heading h1:after{content:'';display:block;width:130px;max-width:60%;height:5px;border-radius:4px;background:#e5c4a1;margin-top:13px}.page-heading p{font-size:18px;color:#607f90;line-height:1.5;margin:13px 0 0}.header-sticker{object-fit:contain;width:120px;height:140px;flex:0 0 120px;pointer-events:none}.workspace-toolbar{display:flex;align-items:center;justify-content:space-between;gap:14px;margin-bottom:27px}.mode-switch{display:flex;gap:4px;padding:5px;border:1px solid #dce3e4;border-radius:17px;background:#f3f3ee}.mode-switch button{background:transparent;border:1px solid transparent;border-radius:12px;padding:11px 17px;font-size:15px;line-height:1.5;font-weight:700;color:#637b86}.mode-switch button[aria-pressed=true]{background:#fff;border-color:#d9e3e7;color:#254f65;box-shadow:0 2px 6px #15384d05}#toolbar-meta{font-size:15px;color:var(--muted);text-align:right;line-height:1.5}.content-layout{display:grid;grid-template-columns:minmax(0,1fr) 224px;gap:24px;align-items:start}.task-area{min-width:0}.topic-heading{display:flex;align-items:flex-start;justify-content:space-between;gap:16px;margin-bottom:18px;min-height:35px}.topic-heading h2{min-width:0;flex:1}.topic-heading>span{font-size:15px;color:var(--muted);padding-top:7px;white-space:nowrap}.task-tabs{display:flex;flex-wrap:wrap;gap:8px;margin-bottom:17px}.task-tab{position:relative;background:white;border:1px solid #d8e1e5;border-radius:12px;min-width:41px;min-height:38px;font-size:16px;padding:7px 10px}.task-tab.active{background:var(--accent);border-color:var(--accent);color:#fff}.task-tab.correct:after,.task-tab.wrong:after{content:'';position:absolute;width:7px;height:7px;right:2px;top:2px;border-radius:50%;border:1px solid white;background:#608e72}.task-tab.wrong:after{background:#c18062}.task-card,.teacher-task{background:#fff;border:1px solid #dbe3e6;border-radius:22px;padding:24px;box-shadow:0 4px 18px #324b5904}.task-top{display:flex;align-items:center;flex-wrap:wrap;gap:10px;margin-bottom:21px}.task-label{font-size:16px;font-weight:800;color:#386078}.task-status{font-size:14px;background:#edf3f5;padding:5px 9px;border-radius:20px;color:#67818d}.task-top .text-button{margin-left:auto}.text-button{border:0;background:transparent;padding:6px 0;font-size:15px;color:#527b92;text-decoration:underline;text-underline-offset:4px;line-height:1.6}.source-image-wrap{overflow-x:auto;max-width:100%;background:#fff;scrollbar-width:thin;margin:0 0 16px}.source-task-image{display:block;width:100%;height:auto;object-fit:contain;max-width:none}.selection-help{font-size:16px;line-height:1.6;color:var(--muted);margin:23px 0 12px}.answer-numbers{display:flex;gap:10px;flex-wrap:wrap;margin:0 0 23px}.element{background:#edf4f7;border:1px solid #d5e2e9;border-radius:12px;width:43px;min-height:43px;font-size:19px;font-weight:700}.element[aria-pressed=true]{background:#d4e8f3;outline:2px solid #688da2;outline-offset:2px}.element:nth-child(2){background:#f8eee1}.element:nth-child(3){background:#eaf1eb}.element:nth-child(4){background:#f5f0df}.element:nth-child(5){background:#f5ebed}#answer-form{border-top:1px solid #e7ecee;padding-top:22px;display:flex;align-items:flex-end;justify-content:space-between;gap:14px;flex-wrap:wrap}.answer-label{display:flex;flex-direction:column;gap:9px;font-size:16px;font-weight:800}.answer-label input{border:1px solid #bfcfd8;border-radius:12px;background:#fbfcfd;width:145px;height:45px;padding:10px 12px;font-size:19px}.answer-label input::placeholder{font-size:14px;color:#8b9ba4}.button{display:inline-flex;justify-content:center;align-items:center;text-align:center;gap:7px;border:1px solid transparent;border-radius:13px;padding:11px 16px;font-size:16px;font-weight:700;line-height:1.5;min-height:45px;max-width:100%}.primary{background:var(--accent);color:white}.outline{background:#ffffff99;border-color:#c7d8e1;color:#3d6881}.plain{background:transparent;color:#5f7b8c;padding-left:0}.answer-help{font-size:14px;color:var(--muted);line-height:1.5;margin:11px 0 20px}#feedback{padding:13px 15px;border-radius:12px;background:#fcf1dc;font-size:16px;line-height:1.6;margin:15px 0;color:#846339}#feedback.correct{background:#eaf3ec;color:#4f765a}#feedback.wrong{background:#faeee6;color:#956146}#explanation{border-top:1px solid #e5ecef;padding-top:16px;color:#416e87;font-size:16px}#explanation summary{cursor:pointer;font-weight:800}#explanation-body{font-size:18px;color:var(--ink);line-height:1.7;padding-top:15px}#explanation-body strong{display:block;color:#416e87;margin-bottom:7px}.task-navigation{display:flex;justify-content:space-between;gap:14px;margin:21px 0 30px}.rail{display:flex;flex-direction:column;gap:20px;min-width:0}.progress-card,.collection-card,.note-card{border:1px solid #d6e2e5;background:#e7f0f4;border-radius:22px;padding:23px 20px}.progress-card .mini-label{color:#6b8c9d}.progress-value{display:flex;align-items:center;gap:12px;margin:20px 0 16px}.progress-value strong{font-family:Arial,Helvetica,sans-serif;font-size:43px;font-weight:700;line-height:1.2;color:#3d6b83}.progress-value span{font-size:15px;line-height:1.6;color:#688391}progress{display:block;width:100%;height:6px;border:0;border-radius:4px;overflow:hidden;background:#d0e0e8}progress::-webkit-progress-bar{background:#d0e0e8}progress::-webkit-progress-value{background:#7699ad}progress::-moz-progress-bar{background:#7699ad}.topic-progress-inline{display:flex;gap:12px;justify-content:space-between;font-size:15px;line-height:1.5;margin:18px 0}.progress-card .button,.collection-card .button{width:100%;font-size:15px;padding:10px}.progress-card>.text-button{display:block;text-align:left;margin-top:12px}.progress-card small,.collection-card small{display:block;font-size:14px;line-height:1.6;margin-top:17px;color:var(--muted)}#mistake-message{font-size:15px;line-height:1.6;margin-top:10px}.note-card{background:#f6ecdb;border:1px dashed #d9c49f}.note-top{display:flex;align-items:center;justify-content:space-between;gap:8px;margin-bottom:12px}.note-top .mini-label{font-size:12px;letter-spacing:1px}.note-sticker{display:block;object-fit:contain;width:62px;height:78px;flex-shrink:0}.note-card p{font-size:17px;line-height:1.75;color:#7e6d57;margin:0}.collection-card{background:#edf3f4}.collection-card h3{font-size:25px;margin:16px 0}.collection-card>p{font-size:16px;line-height:1.6;color:var(--muted)}#selected-list{list-style:none;padding:0;margin:0 0 16px;max-height:340px;overflow:auto}#selected-list li{display:flex;gap:6px;justify-content:space-between;align-items:flex-start;padding:10px 0;border-bottom:1px solid #d8e4e7;font-size:15px;line-height:1.5}#selected-list li span{min-width:0;overflow-wrap:break-word}.remove-task{border:0;background:none;font-size:23px;padding:0 4px;color:#718894;flex-shrink:0}.teacher-toolbar{display:flex;justify-content:space-between;align-items:center;gap:14px;flex-wrap:wrap;padding:15px 18px;background:#f0f5f6;border:1px solid #dae5e9;border-radius:15px}.check-label{display:flex;align-items:center;gap:12px;line-height:1.6;font-size:16px;cursor:pointer;min-width:0}.check-label input{accent-color:#527e95;width:20px;height:20px;flex-shrink:0;cursor:pointer}.teacher-help{font-size:16px;color:var(--muted);line-height:1.6;margin:16px 0 20px}#teacher-list{display:grid;gap:18px;margin-bottom:30px}.teacher-task.selected{border-color:#8aafc1;box-shadow:0 0 0 1px #a8c4d0}.teacher-task-top{display:flex;align-items:flex-start;justify-content:space-between;gap:16px;margin-bottom:23px}.teacher-task-top .check-label{align-items:flex-start;font-weight:800}.teacher-task-top .check-label input{margin-top:3px}.teacher-task-top small{display:block;font-size:14px;font-weight:400;color:var(--muted);line-height:1.6;margin-top:4px}.teacher-task-top .text-button{flex-shrink:0}.teacher-task .source-image-wrap{margin-bottom:0}.progress-heading{display:flex;align-items:center;justify-content:space-between;gap:24px;margin:10px 0 25px}.progress-heading .eyebrow{display:block;margin-bottom:10px}.progress-stats{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:14px;margin-bottom:24px}.progress-stats>div{border:1px solid #dbe4e7;background:#e5eff4;border-radius:20px;padding:21px 20px;min-width:0}.progress-stats>div:nth-child(2){background:#f5e7da}.progress-stats>div:nth-child(3){background:#f2eddd}.progress-stats>div:nth-child(4){background:#e8efe8}.progress-stats span{font-size:16px;font-weight:700;line-height:1.5;display:block}.progress-stats strong{font-family:Arial,Helvetica,sans-serif;font-size:32px;line-height:1.4;display:block;margin:14px 0 7px}.progress-stats small{display:block;line-height:1.5;font-size:14px;color:var(--muted)}.topic-progress-list{background:#fff;border:1px solid #dce5e8;border-radius:22px;padding:3px 24px}.topic-progress-row{display:grid;grid-template-columns:minmax(0,1fr) auto;gap:26px;align-items:center;padding:22px 0;border-bottom:1px solid #e6ecef}.topic-progress-row:last-child{border:0}.progress-title-row{display:flex;justify-content:space-between;align-items:flex-start;gap:16px;margin-bottom:14px}.progress-title-row h3{font-size:19px;line-height:1.5}.progress-fraction{white-space:nowrap;font-size:16px;color:var(--muted)}.topic-progress-row p{font-size:15px;line-height:1.5;color:var(--muted);margin:11px 0 0}.progress-footnote{color:var(--muted);font-size:15px;line-height:1.7;margin:18px 0}.storage-notice{padding:15px;background:#fcf0d7;border-radius:12px;font-size:16px;line-height:1.6;margin:20px 0}footer{display:flex;justify-content:space-between;gap:16px;border-top:1px solid #e0e0d6;padding:22px 0;margin-top:15px;font-size:14px;line-height:1.6;color:#81929a}footer span:first-child{font-weight:700}dialog{border:1px solid #d7e2e6;border-radius:23px;color:var(--ink);background:#fcfaf6;padding:27px;width:min(980px,94vw);max-height:90vh;overflow:auto}dialog::backdrop{background:#243d4c80;backdrop-filter:blur(3px)}.dialog-heading{display:flex;justify-content:space-between;align-items:flex-start;gap:18px}.dialog-heading h2{margin-top:7px}.dialog-heading>.button{flex-shrink:0}.print-actions{display:flex;flex-wrap:wrap;gap:12px;margin-top:23px}.print-help,.image-hint{font-size:15px;line-height:1.7;color:var(--muted)}.print-task{border-bottom:1px solid #dae4e8;padding:24px 0;break-inside:avoid}.print-task>strong{font-size:19px}.print-source-image{display:block;width:100%;height:auto;margin:18px 0}.print-key{line-height:1.7;padding:16px 0;border-bottom:1px solid #dce5e8;break-inside:avoid}.image-zoom-scroll{overflow:auto;margin-top:20px;background:white}.image-zoom-scroll img{display:block;width:100%;min-width:950px;height:auto;max-width:none}#image-dialog{width:min(1200px,96vw)}#print-area{display:none}
@media(min-width:1450px){main{padding-left:48px;padding-right:48px}.content-layout{grid-template-columns:minmax(0,1fr) 250px;gap:28px}.task-card,.teacher-task{padding:30px}.rail{gap:23px}}
@media(max-width:1150px){.layout{grid-template-columns:230px minmax(0,1fr)}.sidebar{padding:28px 14px}main{padding:26px 24px 0}.content-layout{grid-template-columns:minmax(0,1fr) 190px;gap:18px}.header-note{font-size:20px}.header{gap:15px}.brand{font-size:20px}.page-heading{padding:23px}.header-sticker{width:92px;flex-basis:92px;height:115px}.mode-switch button{padding:10px 12px;font-size:14px}.progress-card,.collection-card,.note-card{padding:21px 16px}.task-card,.teacher-task{padding:21px}.progress-stats{grid-template-columns:repeat(2,minmax(0,1fr))}.progress-heading{align-items:flex-start}.topic-heading h2{font-size:22px}.header-note{margin-left:auto}.note-top{flex-wrap:wrap}}
@media(max-width:960px){.content-layout{grid-template-columns:minmax(0,1fr)}.rail{display:grid;grid-template-columns:1fr 1fr;gap:18px;margin-bottom:25px;align-items:stretch}.header-note{display:none}.demo{margin-left:auto}.workspace-toolbar{flex-wrap:wrap}.workspace-toolbar #toolbar-meta{display:none}.mode-switch{width:100%}.mode-switch button{flex:1}.page-heading{gap:14px}.page-heading p{font-size:16px}.header-sticker{width:75px;flex-basis:75px;height:102px}.teacher-task-top{gap:12px}.progress-heading{flex-wrap:wrap}.topic-progress-row{gap:16px}.topic-progress-list{padding:3px 20px}.progress-title-row h3{font-size:18px}.note-top{flex-wrap:nowrap}.progress-value{margin:18px 0}.topic-button{font-size:16px}.collection-card{grid-column:1}.note-card{grid-column:2}.source-task-image{min-width:540px}}
@media(max-width:700px){.header{min-height:85px;padding:16px 18px}.brand{font-size:18px;gap:10px}.brand-mark{width:39px;height:39px;font-size:28px;border-radius:13px}.brand small{font-size:12px;letter-spacing:1.5px}.demo{font-size:14px;padding:6px 11px}.layout{display:flex;flex-direction:column}.sidebar{padding:17px 18px 10px;border-right:0;border-bottom:1px solid #e0e1d7}.side-caption{font-size:12px}.line-card,.sidebar-foot{display:none}#topics{display:flex;gap:8px;overflow-x:auto;padding:12px 2px 6px;scrollbar-width:thin}.topic-button{width:204px;min-height:101px;flex:0 0 204px;padding:11px 12px;border:1px solid #e1e5e2;background:#fdfbf7;font-size:15px;grid-template-columns:18px minmax(0,1fr)}.topic-button small{font-size:13px}.topic-number{font-size:13px}main{padding:21px 17px 0}.breadcrumbs{font-size:14px}.page-heading{padding:21px 19px;margin:20px 0 22px;gap:10px;border-radius:21px}.page-heading h1{font-size:27px;letter-spacing:-.5px}.page-heading p{font-size:16px;line-height:1.7}.header-sticker{width:66px;flex:0 0 66px;height:95px}.workspace-toolbar{margin-bottom:22px}.mode-switch{padding:4px;gap:2px;border-radius:14px}.mode-switch button{padding:9px 7px;font-size:13px;line-height:1.7;min-width:0}.topic-heading{gap:12px;margin-bottom:17px}.topic-heading h2{font-size:22px}.topic-heading>span{font-size:14px}.task-card,.teacher-task{border-radius:20px;padding:20px 17px}.task-top{gap:8px;margin-bottom:18px}.task-label{font-size:15px}.task-status{font-size:13px}.task-top .text-button{font-size:14px}.source-image-wrap{padding-bottom:10px;margin-bottom:10px}.source-task-image{min-width:0;width:100%}.selection-help{font-size:15px;line-height:1.7;margin-top:17px}.answer-numbers{gap:9px}.element{width:42px;min-height:42px}.button{font-size:15px;padding:11px 13px}.answer-label input{width:135px}.rail{gap:14px}.progress-card,.collection-card,.note-card{padding:20px 15px;border-radius:20px}.mini-label{font-size:12px;letter-spacing:1.2px}.progress-value strong{font-size:37px}.progress-value{gap:9px}.progress-value span{font-size:14px}.topic-progress-inline{font-size:14px}.progress-card .button{font-size:14px;padding:9px}.note-card p{font-size:16px;line-height:1.7}.note-sticker{width:53px;height:70px}.note-top{gap:4px}.note-top .mini-label{font-size:12px}.progress-card small,.collection-card small{font-size:13px}.collection-card h3{font-size:22px}.teacher-toolbar{padding:12px 14px;gap:8px}.check-label{font-size:15px}.teacher-toolbar .text-button{font-size:14px}.teacher-help{font-size:15px}.teacher-task-top{gap:10px}.teacher-task-top .text-button{font-size:14px}.teacher-task-top small{font-size:14px}.teacher-task-top .check-label{gap:9px}.progress-heading h2{font-size:25px}.progress-stats{gap:11px}.progress-stats>div{padding:19px 16px;border-radius:17px}.progress-stats span{font-size:15px}.progress-stats strong{font-size:29px}.progress-stats small{font-size:13px}.topic-progress-row{grid-template-columns:1fr;gap:13px;padding:20px 0}.topic-progress-row .button{justify-self:start;min-height:40px}.topic-progress-list{padding:0 18px;border-radius:20px}.progress-title-row h3{font-size:18px}.topic-progress-row p{font-size:14px}.progress-footnote{font-size:14px}footer{flex-direction:column;gap:5px;font-size:13px}dialog{padding:21px 17px;border-radius:20px}.dialog-heading{gap:13px}.dialog-heading h2{font-size:22px}.dialog-heading>.button{font-size:14px;padding:9px 12px}.print-task{padding:21px 0}.print-source-image{margin:14px 0}}
@media(max-width:390px){.brand{font-size:16px}.brand-mark{width:34px;height:34px;font-size:26px}.brand small{font-size:12px}.demo{font-size:13px;padding:6px 9px}.page-heading{gap:8px;padding:20px 16px}.page-heading h1{font-size:26px}.header-sticker{width:50px;flex-basis:50px;height:80px}.mode-switch button{font-size:12px;padding:8px 6px}.rail{grid-template-columns:1fr}.note-card,.collection-card{grid-column:1}.note-top{justify-content:flex-start;gap:20px}.progress-card .button{font-size:15px}.task-navigation .button{font-size:14px}.task-top .text-button{margin-left:0}.progress-stats>div{padding:17px 13px}.progress-stats strong{font-size:25px}}
@media(prefers-reduced-motion:reduce){*{transition:none!important;scroll-behavior:auto!important}}
@media print{@page{size:A4;margin:18mm}body{background:#fff;color:#111;font-size:12pt}body>*{display:none!important}body>#print-area{display:block!important}#print-area h1{font-size:23pt;line-height:1.4;margin-bottom:7mm}#print-area .print-task{padding:7mm 0;border-color:#ddd}#print-area .print-source-image{width:100%;height:auto;min-width:0;margin:4mm 0}#print-area .print-key{border-color:#ddd}dialog[open]{display:none!important}}

/* Line catalog and creator channels */
.line-navigation{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:12px;margin:0 0 22px}.line-link{display:flex;flex-direction:column;gap:7px;min-width:0;padding:15px 16px;text-decoration:none;border:1px solid var(--line);border-radius:18px;background:#fdfbf7;line-height:1.5}.line-link strong{font-family:Arial,Helvetica,sans-serif;font-size:17px}.line-link span{font-size:16px;overflow-wrap:break-word}.line-link.active{background:var(--blue);border-color:#86aabd;box-shadow:inset 0 0 0 1px #86aabd}.social-top{display:flex;align-items:center;justify-content:space-between;flex-wrap:wrap;gap:10px;margin-bottom:20px;font-size:16px;color:var(--muted)}.social-links{display:flex;gap:10px 18px;flex-wrap:wrap;align-items:center}.social-links a{font-size:16px;text-decoration:none;color:var(--accent);border-bottom:1px solid #b8cbd3;padding:4px 0}.social-links a:hover{text-decoration:underline}.page-heading{margin-top:0}.page-heading h1{max-width:760px}.eyebrow{text-transform:uppercase}
@media(max-width:1100px){.line-navigation{grid-template-columns:repeat(2,minmax(0,1fr))}}@media(max-width:700px){.line-navigation{gap:9px;margin-bottom:16px}.line-link{padding:12px;border-radius:15px;gap:5px}.line-link strong{font-size:16px}.line-link span{font-size:15px}.social-top{margin-bottom:16px;font-size:15px}.social-links{gap:9px 16px}.social-links a{font-size:16px}.page-heading h1{font-size:25px;line-height:1.4}}

@media(max-width:700px){.line-navigation{grid-template-columns:repeat(4,minmax(0,1fr));gap:7px}.line-link{padding:11px 5px;text-align:center;align-items:center;border-radius:12px}.line-link strong{font-size:15px;white-space:nowrap}.line-link span{display:none}.page-heading{position:relative;display:block;padding:18px;margin:0 0 18px}.page-heading h1{font-size:25px;line-height:1.4}.page-heading p{margin-right:42px}.header-sticker{position:absolute;right:12px;bottom:9px;width:42px;height:50px}.topic-button{width:238px;flex-basis:238px;min-height:83px}.social-top>span{display:none}}

.account-open{white-space:nowrap;font-size:16px;text-decoration:none}.header{flex-wrap:wrap}.account-panel{border:1px solid #cddfe8;background:#edf4f7;border-radius:20px;padding:18px 21px;margin-bottom:21px;display:flex;gap:12px 20px;align-items:center;flex-wrap:wrap;scroll-margin-top:15px}.account-panel>div:first-child{flex:1 1 220px;min-width:0}.account-panel strong{font-size:19px;overflow-wrap:anywhere}.account-panel p{font-size:16px;line-height:1.6;margin:5px 0 0}.account-actions{display:flex;flex-wrap:wrap;gap:10px;align-items:center}.account-actions a{text-decoration:none}.account-actions .button{font-size:16px}.account-panel #sync-status{flex-basis:100%;color:var(--muted);margin:0}.account-panel #sync-status.error{color:#904128}.teacher-toolbar{align-items:end;flex-wrap:wrap}.teacher-filter{display:flex;flex:1 1 190px;min-width:0;flex-direction:column;gap:6px;font-size:16px}.teacher-filter select{width:100%;min-width:0;font:inherit;color:var(--ink);background:white;border:1px solid #c7d7df;border-radius:12px;padding:11px 10px;text-overflow:ellipsis}.teacher-filter select:disabled{opacity:.55}.teacher-line-heading{margin:25px 0 16px;font-size:20px}.collection-lines{font-size:16px;line-height:1.6;color:var(--muted)}.teacher-task-top .check-label{min-width:0}.teacher-task-top .check-label span{min-width:0;overflow-wrap:anywhere}
@media(max-width:700px){.account-open{margin-left:auto;font-size:15px;padding:9px 12px}.header-note{display:none}.account-panel{padding:16px;border-radius:17px}.account-panel strong{font-size:18px}.account-actions{width:100%}.account-actions .button{font-size:15px}.account-panel p{font-size:15px}.teacher-filter{flex-basis:100%}.teacher-line-heading{font-size:19px}.teacher-toolbar>.text-button{margin-top:4px}}

#login-dialog{width:min(560px,calc(100vw - 32px));max-width:100%;box-sizing:border-box;max-height:90dvh;overflow:auto;padding:clamp(20px,4vw,36px);border-radius:26px}
#login-dialog::backdrop{background:rgba(35,63,80,.35)}
#login-dialog .dialog-heading{flex-wrap:wrap;gap:12px;align-items:center}
#login-dialog h2{font-size:1.5rem;overflow-wrap:anywhere;margin:0}
#login-dialog p{line-height:1.6;overflow-wrap:anywhere}
#login-form label{display:block;margin:16px 0 8px;font-weight:700}
#login-form input{width:100%;min-width:0;box-sizing:border-box;border:1px solid #a6bdc9;border-radius:14px;padding:14px;font:inherit;font-size:1rem;color:#233f50;background:#fff}
#login-form input:focus{outline:3px solid #bddbea;outline-offset:2px}
#login-form input[readonly]{background:#f1f5f7}
#login-code{letter-spacing:.15em}
.login-buttons{display:flex;gap:10px;flex-wrap:wrap}
.login-buttons .button{white-space:normal;overflow-wrap:anywhere}
#login-message.error{color:#963e36}
.login-hint{font-size:.875rem}
#account-title{overflow-wrap:anywhere}
@media print{#login-dialog{display:none!important}}

/* Scientific masthead: one coherent illustration of nitrogen's electronic structure. */
:root{--ink:#25364a;--muted:#536879;color:#25364a;font-family:Arial,Helvetica,sans-serif;font-size:18px}
body{line-height:1.5}h1,h2,h3{font-family:Arial,Helvetica,sans-serif;font-weight:700}
.research-header{display:grid;grid-template-columns:minmax(310px,1fr) minmax(360px,1.15fr) auto;gap:28px;align-items:center;padding:23px max(28px,4%);min-height:170px;background:#1b2c46;border-bottom:3px solid #7e9ab7;color:#f6f7fc;position:relative;isolation:isolate}
.research-header:before{content:"";position:absolute;inset:0;z-index:-1;pointer-events:none;background:linear-gradient(110deg,#21395580,transparent 50%,#38446b50)}
.identity-block{min-width:0}.research-header .brand{gap:13px;font:700 28px/1.2 Arial,Helvetica,sans-serif;letter-spacing:-.65px;color:#fff;min-width:0;flex-shrink:1}
.research-header .brand small{font:600 13px/1.4 Arial,Helvetica,sans-serif;letter-spacing:2.6px;color:#bdd0e7;margin-top:10px}
.orbital-mark{width:56px;height:56px;flex:0 0 56px}
.research-tagline{font-size:17px;line-height:1.5;color:#d0dced;margin:15px 0 0;letter-spacing:.1px}
.orbital-study{display:flex;align-items:center;justify-content:center;gap:22px;border-left:1px solid #9daecc4d;border-right:1px solid #9daecc4d;padding:0 22px;min-width:0}
.orbital-drawing{display:block;width:130px;height:126px;flex:0 0 130px;overflow:visible}
.electron-study{min-width:0}.configuration{display:flex;align-items:center;gap:16px;white-space:nowrap;margin:0 0 12px;line-height:1.2;color:#e7edfc}
.configuration strong{font-size:30px;font-weight:500;color:#b6dcdf}.configuration>span{font-size:22px;letter-spacing:.4px}.configuration sup{font-size:.65em;line-height:0;position:relative;vertical-align:baseline;top:-.55em}
.orbital-levels{display:flex;gap:14px;align-items:start}.orbital-level{display:flex;flex-direction:column;align-items:center;gap:3px}.p-boxes{display:flex;gap:0}.orbital-box{display:block;width:31px;height:32px;border:1px solid #9cb3d5;position:relative;background:#9ebcde0a}.p-boxes .orbital-box+.orbital-box{border-left:0}.orbital-box svg{display:block;width:100%;height:100%;fill:none;stroke:#e4edff;stroke-width:1.4;stroke-linecap:round;stroke-linejoin:round}.p-level .orbital-box svg{stroke:#a8dadd}.level-label{font-size:14px;color:#b8cbe4;line-height:1.4}
.research-header .account-open{display:flex;align-items:center;justify-content:center;gap:9px;padding:13px 16px;margin:0;background:#eef2fc;color:#203652;border:1px solid #e4eaf8;border-radius:10px;white-space:nowrap;font-size:16px;line-height:1.4;font-weight:600;box-shadow:none;text-decoration:none}
.research-header .account-open:hover{background:#dbe5f6}.research-header .account-open svg{fill:none;stroke:currentColor;stroke-width:1.7;stroke-linecap:round;flex-shrink:0}.research-header a:focus-visible{outline:3px solid #9dd9e3;outline-offset:5px}
.side-caption,.mini-label,.eyebrow{letter-spacing:1.2px}.topic-number{line-height:24px}.line-card div>span{line-height:1.5}.line-link span{line-height:1.5}.account-panel p{line-height:1.6}.answer-help,.selection-help{line-height:1.6}.page-heading{padding:25px 28px}.page-heading h1{font-size:clamp(30px,3vw,42px);line-height:1.25;letter-spacing:-.65px}.page-heading p{font-size:18px}.sidebar-foot p{font-size:20px;font-style:normal}.mode-switch button{font-family:Arial,Helvetica,sans-serif;font-size:15px}.topic-heading h2{font-size:25px}
@media(min-width:1550px){.research-header{gap:36px;grid-template-columns:minmax(380px,1fr) minmax(420px,1.1fr) auto}.research-header .brand{font-size:32px}.orbital-study{gap:32px}.configuration>span{font-size:25px}.orbital-box{width:36px;height:36px}.research-tagline{font-size:19px}}
@media(max-width:1190px){.research-header{grid-template-columns:minmax(285px,1fr) minmax(320px,1fr) auto;gap:17px;padding:22px 25px}.research-header .brand{font-size:25px;gap:10px}.orbital-mark{width:49px;height:49px;flex-basis:49px}.research-tagline{font-size:16px}.orbital-study{gap:13px;padding:0 16px}.orbital-drawing{width:108px;flex-basis:108px}.configuration{gap:12px}.configuration>span{font-size:20px}.orbital-levels{gap:9px}.orbital-box{width:29px;height:31px}.research-header .account-open{font-size:15px;padding:12px}}
@media(max-width:1000px){.research-header{grid-template-columns:minmax(0,1fr) auto;gap:20px;padding:23px 28px}.research-header .brand{font-size:29px}.research-header .account-open{grid-row:1;grid-column:2}.orbital-study{grid-row:2;grid-column:1/-1;justify-content:center;border:0;border-top:1px solid #9daecc4d;padding:13px 0 0;gap:28px}.orbital-drawing{width:140px;height:112px;flex-basis:140px}.configuration>span{font-size:24px}.orbital-levels{gap:17px}.orbital-box{width:34px;height:34px}.research-tagline{font-size:17px;margin-top:10px}.research-header .brand small{font-size:12px;margin-top:8px}}
@media(max-width:700px){.research-header{padding:20px 18px;gap:18px 12px}.research-header .brand{font-size:23px;letter-spacing:-.5px}.research-header .brand small{font-size:11px;letter-spacing:2px}.orbital-mark{width:45px;height:45px;flex-basis:45px}.research-tagline{font-size:15px;max-width:260px}.research-header .account-open{font-size:14px;padding:11px 12px;max-width:128px;white-space:normal;text-align:left}.research-header .account-open svg{width:17px;height:17px}.orbital-study{gap:23px}.orbital-drawing{width:122px;flex-basis:122px;height:112px}.configuration>span{font-size:22px}.configuration strong{font-size:29px}.orbital-box{width:32px;height:32px}.orbital-levels{gap:13px}.page-heading{padding:21px 19px}.page-heading h1{font-size:29px;line-height:1.25}.page-heading p{font-size:17px;margin-right:0}.mode-switch button{font-size:14px;padding:10px 7px}.topic-heading h2{font-size:23px}.line-link strong{font-size:15px}.line-link{padding:12px 4px}.topic-button{width:256px;flex-basis:256px}.topic-button small{font-size:13px}.task-tab{min-width:43px;min-height:42px}.answer-label input{font-size:18px}}
@media(max-width:420px){.research-header{padding:19px 16px;gap:16px 9px}.research-header .brand{font-size:22px;gap:8px}.research-header .brand>span{max-width:160px}.orbital-mark{width:40px;height:40px;flex-basis:40px}.research-header .brand small{font-size:10px;letter-spacing:1.5px;margin-top:6px}.research-tagline{font-size:15px;margin-top:11px}.research-header .account-open{font-size:13px;max-width:104px;padding:11px 10px}.research-header .account-open svg{display:none}.orbital-study{gap:17px}.orbital-drawing{width:101px;flex-basis:101px;height:105px}.configuration{gap:12px}.configuration>span{font-size:20px}.orbital-box{width:29px;height:31px}.orbital-levels{gap:10px}.page-heading h1{font-size:27px}.mode-switch button{font-size:13px}.line-link strong{font-size:14px}.line-navigation{gap:5px}}
@media(max-width:359px){.research-header{padding-inline:12px;gap:15px 7px}.research-header .brand{font-size:20px}.orbital-mark{width:34px;height:34px;flex-basis:34px}.research-header .account-open{max-width:90px;font-size:12px}.research-tagline{font-size:14px}.orbital-study{gap:10px}.orbital-drawing{width:92px;flex-basis:92px}.configuration>span{font-size:19px}.orbital-levels{gap:8px}.orbital-box{width:27px;height:30px}}

/* One generated artwork, with an independent accessible account control. */
.image-header{display:block;position:relative;min-height:0;padding:0;background:#111e34;border-bottom:1px solid #647490;overflow:hidden}
.masthead-home{display:block;text-decoration:none}.masthead-art{display:block;width:100%;max-width:none;height:clamp(260px,25vw,410px);object-fit:cover;object-position:center}
.image-header .account-open{position:absolute;top:22px;right:4%;display:flex;align-items:center;gap:9px;margin:0;padding:12px 17px;min-height:44px;background:#f3f4fcf2;border:1px solid #fff9;border-radius:10px;color:#23364d;box-shadow:0 3px 14px #09112335;font:600 16px/1.4 Arial,Helvetica,sans-serif;text-decoration:none;white-space:nowrap}
.image-header .account-open:hover{background:#fff}.image-header .account-open svg{fill:none;stroke:currentColor;stroke-width:1.7;stroke-linecap:round;flex-shrink:0}.image-header a:focus-visible{outline:3px solid #b4deed;outline-offset:-4px}
/* Keep the full artwork visible; reserve a separate row for the mobile account link. */
@media(max-width:700px){
  .masthead-art{height:auto;object-fit:contain;object-position:center}
  .image-header .account-open{position:static;width:fit-content;max-width:calc(100% - 32px);margin:8px 16px 16px auto;padding:10px 14px;font-size:14px;min-height:44px;gap:7px;white-space:normal}
  .image-header .account-open svg{width:16px;height:16px}
}

/* Light editorial artwork and a complete, uncropped desktop message. */
.image-header{background:#f5f0f5;border-bottom-color:#d9cfe1}
.image-header .account-open{background:#5a496b;color:#fff;border-color:#5a496b;box-shadow:0 3px 12px #5a496b20}
.image-header .account-open:hover{background:#493959;border-color:#493959}
.image-header a:focus-visible{outline-color:#7d5e94}
@media(min-width:701px){.masthead-home{max-width:1800px;margin-inline:auto}.masthead-art{height:auto;object-fit:contain}}


/* Unverified answers are neutral, never styled as errors or successes. */
.task-tab.pending, #feedback.pending { background: #f0edf4; color: #655d72; border-color: #d9d3e2; }