@import url('https://fonts.googleapis.com/css2?family=DM+Sans:wght@400;500;600;700&family=Space+Grotesk:wght@400;500;600&display=swap');
*{box-sizing:border-box}body{margin:0;background:#fafbfe;color:#283247;font:14px 'DM Sans',sans-serif}button,textarea{font:inherit}button{cursor:pointer}header{height:80px;padding:0 40px;display:flex;align-items:center;justify-content:space-between;border-bottom:1px solid #edf0f6;background:#fff}.brand{display:flex;align-items:center;gap:10px;text-decoration:none;color:#27324b;font:600 21px 'Space Grotesk',sans-serif}.brand span,.symbol{background:#5962e9;color:#fff;display:grid;place-items:center;border-radius:12px;font-size:30px;width:38px;height:38px}header button{border:1px solid #e7eaf2;background:#fff;color:#728098;border-radius:8px;padding:10px 14px;font-size:12px}main{max-width:800px;margin:auto;padding:35px 24px 210px}#welcome{text-align:center;padding-top:9vh}.symbol{margin:auto;width:56px;height:56px;font-size:43px;border-radius:17px;box-shadow:0 8px 25px #5962e91a}h1{font:500 36px 'Space Grotesk',sans-serif;letter-spacing:-1.3px;margin:25px 0 13px}#welcome p{color:#8c97aa;line-height:1.8}.suggestions{display:grid;grid-template-columns:repeat(4,1fr);gap:10px;margin:35px 0}.suggestions button{padding:17px 12px;text-align:left;border:1px solid #e8ebf4;border-radius:11px;color:#626dd7;background:white;font-size:12px}.suggestions small{display:block;color:#98a2b3;font-size:10px;margin-top:7px}.suggestions button:hover{border-color:#a0a6ee;background:#f6f7ff}.composer-wrap{position:fixed;bottom:0;left:0;right:0;background:linear-gradient(transparent,#fafbfe 20%);padding:25px 24px 14px}form{max-width:752px;margin:auto;background:#fff;border:1px solid #dfe4f0;border-radius:17px;box-shadow:0 6px 35px #3447740b;padding:15px 17px}textarea{display:block;width:100%;border:0;outline:0;resize:none;min-height:50px;max-height:140px;line-height:1.7;color:#34415e;background:none}textarea::placeholder{color:#a1aabb}.composer-bottom{display:flex;align-items:center;justify-content:space-between}#help{border:0;background:none;color:#929db1;font-size:11px;padding:8px 0}.send{width:35px;height:35px;border:0;border-radius:10px;background:#5962e9;color:#fff;font-size:23px}.footnote{text-align:center;color:#a3adbd;font-size:10px;margin:12px 0 0}.message{margin-bottom:25px;line-height:1.7}.message.user{display:flex;justify-content:flex-end}.bubble{max-width:90%;white-space:pre-wrap;overflow-wrap:anywhere;border-radius:15px 15px 4px 15px;background:#eff0fc;color:#48527b;padding:12px 18px}.answer{display:flex;gap:12px}.avatar{width:29px;height:29px;flex-shrink:0;display:grid;place-items:center;background:#5962e9;color:#fff;border-radius:9px;font:23px serif}.answer-content{min-width:0;flex:1;padding-top:2px}.answer-label{font-size:11px;color:#9aa3b5;margin-bottom:12px}.value{font:500 35px 'Space Grotesk',sans-serif;color:#5360dc}.matrix-scroll{overflow:auto}.matrix{display:table;border-left:2px solid #838aeb;border-right:2px solid #838aeb;border-radius:4px;padding:7px 10px;margin:12px 0}.row{display:table-row}.cell{display:table-cell;text-align:center;padding:5px 13px;font:20px 'Space Grotesk',monospace}.note{font-size:12px;color:#8894a8;line-height:1.8}.error{color:#b35365}.actions button{border:0;background:none;padding:5px 0;font-size:10px;color:#9aa5b8}details{font-size:12px;color:#73819b}summary{cursor:pointer;color:#636ddd;padding:10px 0}.step{border-bottom:1px solid #edf0f6;padding:10px 0}.step .cell{font-size:13px;padding:4px 8px}svg{width:100%;max-width:400px;height:280px;display:block}dialog{max-width:570px;width:calc(100% - 32px);border:1px solid #e1e5f0;border-radius:18px;padding:28px;color:#37435e}dialog::backdrop{background:#26345450;backdrop-filter:blur(3px)}dialog h2{font-family:'Space Grotesk',sans-serif}dialog p{line-height:1.8;color:#8994a7;font-size:12px}.close{float:right;border:0;background:#f2f3fa;border-radius:7px;font-size:21px;color:#7b869b}#examples{display:grid;grid-template-columns:1fr 1fr;gap:7px}#examples button{border:1px solid #ebedf6;padding:9px;border-radius:7px;background:#fafbfe;text-align:left;font:11px monospace;color:#667294;overflow-wrap:anywhere}button:focus-visible,textarea:focus-visible{outline:3px solid #b4bafa;outline-offset:3px}.sr-only{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0,0,0,0)}@media(max-width:600px){header{height:65px;padding:0 20px}.brand{font-size:18px}header button{font-size:10px}main{padding:24px 18px 210px}#welcome{padding-top:6vh}h1{font-size:29px}.suggestions{grid-template-columns:1fr 1fr}.composer-wrap{padding:20px 15px 12px}.footnote{font-size:9px}#examples{grid-template-columns:1fr}}
/* Exercise editor and mathematical option board */
.entry-shell{max-width:752px;margin:auto;background:#fff;border:1px solid #dfe4f0;border-radius:17px;box-shadow:0 6px 35px #3447740b;overflow:hidden}form{border:0;box-shadow:none;border-radius:0}.entry-tools{display:flex;gap:17px;align-items:center}.entry-tools button{border:0;background:none;color:#8b96ab;font-size:11px;padding:8px 0}.entry-tools #toggle-board{color:#6870d9}.welcome-link{border:0;background:none;color:#7880cf;font-size:12px}.board-header{display:flex;align-items:center;justify-content:space-between;font-size:11px;color:#909bb0;padding:12px 15px;border-bottom:1px solid #edf0f7}.board-header button{border:0;background:none;font-size:20px;color:#9ba5b6}.board-tabs{display:grid;grid-template-columns:repeat(4,1fr);background:#fafbff;border-bottom:1px solid #e9ecf5}.board-tabs button{border:0;background:none;border-right:1px solid #e9ecf5;padding:12px;color:#8c96aa;font-size:11px}.board-tabs [aria-selected=true]{background:#eff0ff;color:#5962db;font-weight:600}.board-options{display:grid;grid-template-columns:repeat(7,1fr);gap:6px;padding:12px 15px}.board-options button{display:flex;flex-direction:column;justify-content:center;align-items:center;gap:5px;border:1px solid #e7eaf4;border-radius:6px;background:#fbfcff;color:#586781;min-height:51px;font-size:16px}.board-options button span{font-size:9px;color:#949fb1}.board-options button b{font-family:serif;font-size:18px;font-weight:400}.board-options button:hover,.board-options .selected{border-color:#a5aaeb;background:#f0f1ff;color:#5962db}.board-hint{font-size:10px;color:#9aa5b8;padding:0 15px 10px;margin:0}#board{border-bottom:1px solid #e5e9f3;max-height:55vh;overflow:auto}#builder{padding:3px 15px 15px}.builder-heading{display:flex;align-items:center;justify-content:space-between;color:#66748f;font-size:12px;margin:8px 0 15px}.builder-heading button{border:0;background:none;font-size:10px;color:#9aa5b5}.grid-controls{display:flex;align-items:center;gap:14px;margin:13px 0 9px;font-size:11px;color:#8995a9}.grid-controls>label:first-child{margin-right:auto;color:#65728b}.dimension-label{display:flex;align-items:center;gap:6px;font-size:10px}.dimension-label select{border:1px solid #e5e9f3;padding:4px 7px;background:white;border-radius:4px;color:#7b879d}.editable-matrix{display:grid;gap:7px;overflow:auto;max-width:100%;border-left:2px solid #b3b9ed;border-right:2px solid #b3b9ed;border-radius:5px;padding:8px 11px}.editable-matrix input{width:100%;min-width:45px;border:1px solid #e5e8f1;border-radius:6px;padding:9px 5px;text-align:center;color:#56627c;background:#fbfcff;font:15px monospace}#builder-data{max-height:250px;overflow:auto}#equation-entry{border:1px solid #e6eaf3;border-radius:7px;background:#fafbff;margin-top:10px;padding:12px;font:16px monospace;line-height:1.8;min-height:105px}#builder-data>label{font-size:11px;color:#8693a8}.mini-keys{display:flex;gap:5px;flex-wrap:wrap;margin-top:10px}.mini-keys button{border:1px solid #e5e9f2;background:#fafbff;border-radius:5px;padding:6px 12px;color:#8794aa}.solve-board{border:0;border-radius:7px;background:#5962e9;color:white;padding:10px 15px;margin-top:10px;font-size:12px;width:100%}#builder-error{font-size:11px}.understood{border-left:2px solid #dfe3f7;padding:4px 0 4px 12px;margin:12px 0 22px}.understood span{font-size:10px;color:#9da7b8}.understood p{font-size:12px;color:#8290a6;margin:4px 0}.result-heading{font-size:11px;color:#8b96ab;margin-bottom:10px}.solution-values{color:#626dd0;font:17px 'Space Grotesk'}.explanation{margin:22px 0}.explanation summary{border-top:1px solid #e9edf5;padding:16px 0;font-size:12px}.solution-step{display:flex;gap:12px;margin:16px 0 23px}.step-number{flex-shrink:0;background:#eff1fd;color:#7e87d7;width:24px;height:24px;text-align:center;border-radius:50%;font-size:11px;line-height:24px}.solution-step>div{min-width:0;flex:1}.solution-step strong{font-size:12px;font-weight:600;color:#62718d}.solution-step p{font-size:12px;color:#8593a9;margin:6px 0;line-height:1.8}.solution-step .cell{font-size:15px;padding:5px 10px}.actions{display:flex;gap:18px}.actions .change-data{color:#7b85c3}.error-board{margin-top:10px;border:1px solid #e4e8f4;background:white;border-radius:7px;padding:8px 12px;color:#7b86ca;font-size:11px}input:focus-visible,select:focus-visible{outline:3px solid #b4bafa;outline-offset:2px}main{padding-bottom:215px}.board-open main{padding-bottom:650px}#messages{padding-bottom:20px}[hidden]{display:none!important}@media(max-width:600px){.board-options{grid-template-columns:repeat(4,1fr);padding:10px}.board-tabs button{padding:11px 5px;font-size:10px}.board-options button{min-height:47px}.board-options button span{font-size:8px}#board{max-height:51vh}.board-open main{padding-bottom:640px}.grid-controls{gap:8px}.grid-controls>label:first-child{font-size:10px}.dimension-label{gap:3px}#builder{padding:2px 12px 12px}.entry-tools{gap:15px}}
/* Screen-sized workspace: no document scrolling or overlapping fixed panels. */
html,body{height:100%;height:100dvh;overflow:hidden}body{display:grid;grid-template-rows:62px minmax(0,1fr) auto}header{height:62px;padding:0 25px}.work-area{display:flex;min-height:0;min-width:0;width:100%;max-width:1380px;margin:auto;padding:20px 24px 8px;gap:22px}main,.board-open main{flex:1;min-width:0;min-height:0;max-width:850px;width:100%;padding:0;margin:0 auto;display:flex;flex-direction:column;overflow:hidden}#welcome{flex:1;min-height:0;display:flex;flex-direction:column;justify-content:center;padding:0;margin:auto;width:100%;max-width:750px}.symbol{margin:0 auto;width:48px;height:48px;font-size:36px}h1{font-size:32px;margin:20px 0 8px}#welcome p{margin:8px 0}.suggestions{margin:22px 0 14px}.suggestions button{padding:14px 12px}.composer-wrap{position:static;min-height:0;left:auto;right:auto;bottom:auto;background:#fafbfe;padding:9px 24px 12px}.entry-shell{width:100%;max-width:800px}#composer{padding:12px 16px;max-width:none}#prompt{min-height:42px;height:46px;font-size:13px;max-height:90px}.footnote{margin:8px 0 0;font-size:9px}.work-area #board{width:405px;flex-shrink:0;border:1px solid #e3e7f1;background:white;border-radius:13px;max-height:none;min-height:0;overflow:hidden;display:flex;flex-direction:column}.board-header{flex-shrink:0}.board-tabs{flex-shrink:0}.board-tabs button{padding:11px 5px}.board-options{grid-template-columns:repeat(4,1fr);gap:5px;padding:10px;flex-shrink:0}.board-options button{min-height:42px;gap:3px}.board-options button span{font-size:8px}.board-options button b{font-size:16px}#builder{display:flex;flex-direction:column;min-height:0;flex:1;padding:0 12px 12px}.builder-heading{margin:8px 0 7px;flex-shrink:0}#builder-data{flex:1;min-height:0;max-height:none;overflow:auto;overscroll-behavior:contain}.grid-controls{margin:8px 0}.editable-matrix{padding:6px 8px;gap:5px}.editable-matrix input{padding:7px 3px}.solve-board{flex-shrink:0;margin-top:8px}#builder-error{margin:5px 0 0}#board-hint{padding:8px 12px 15px}#history-bar{display:flex;justify-content:flex-end;align-items:center;gap:13px;color:#939fb1;font-size:10px;height:28px;flex-shrink:0;margin-bottom:8px}#history-bar button,.step-controls button{border:1px solid #e2e6f0;background:white;border-radius:6px;padding:4px 9px;color:#6975cb}button:disabled{opacity:.35;cursor:default}#messages{flex:1;min-height:0;padding:0;display:flex;flex-direction:column;overflow:hidden}.message.user{flex-shrink:0;margin-bottom:12px;max-height:60px}.bubble{padding:8px 13px;font-size:12px;max-height:60px;overflow:auto}.message.answer{flex:1;min-height:0;margin:0;overflow:hidden}.answer-content{display:flex;flex-direction:column;min-height:0;overflow:hidden}.answer-label{margin:0 0 6px;font-size:10px;flex-shrink:0}.understood{margin:0 0 9px;padding:0 0 0 9px;flex-shrink:0}.understood span{font-size:9px}.understood p{margin:2px 0;font-size:11px}.result-heading{font-size:10px;margin:0 0 3px;flex-shrink:0}.value{font-size:31px;flex-shrink:0}.answer-content>.matrix-scroll{max-height:90px;flex-shrink:0}.matrix{margin:6px 0;padding:4px 8px}.cell{font-size:17px;padding:3px 10px}.answer-content>svg{height:135px;flex-shrink:0}.note{margin:5px 0;font-size:11px}.solution-values{margin:3px 0;font-size:14px}.explanation{display:flex;flex-direction:column;flex:1;min-height:0;margin:12px 0 4px;border-top:1px solid #e8ecf4;padding-top:9px;overflow:hidden}.explanation-header{display:flex;justify-content:space-between;align-items:center;gap:10px;flex-shrink:0;margin-bottom:8px}.explanation-header strong{font-size:11px;color:#7783a0;font-weight:500}.step-controls{display:flex;align-items:center;gap:9px;font-size:10px;color:#929cba}.solution-step{margin:0;min-height:0;flex:1;overflow:auto;overscroll-behavior:contain;padding:2px 0}.solution-step p{margin:5px 0;font-size:12px}.solution-step .matrix{margin-top:6px}.actions{flex-shrink:0;gap:14px;margin-top:7px;padding:4px 0}.actions button{font-size:9px}.error{font-size:12px}.error-board{align-self:flex-start}.avatar{width:25px;height:25px;font-size:20px}.answer{gap:10px}dialog{max-height:85dvh;overflow:auto}.welcome-link{margin-top:5px}#welcome[hidden],#board[hidden],.solution-step[hidden],.message[hidden],#history-bar[hidden],#builder[hidden]{display:none!important}
@media(max-width:900px){.work-area{gap:13px;padding:14px 16px 5px}.work-area #board{width:350px}.suggestions{grid-template-columns:1fr 1fr}.board-open #welcome h1{font-size:26px}.board-open #welcome .suggestions{gap:8px}.understood p{font-size:10px}}
@media(max-width:650px){body{grid-template-rows:55px minmax(0,1fr) auto}header{height:55px;padding:0 16px}.brand{font-size:17px}.brand span{width:31px;height:31px;font-size:25px}header button{font-size:9px;padding:8px 10px}.work-area{padding:10px 14px 3px;display:block}.work-area main{height:100%;max-width:none}.board-open .work-area main{display:none}.work-area #board{width:100%;height:100%}.composer-wrap{padding:7px 14px 9px}#composer{padding:10px 12px}#prompt{height:40px;min-height:40px;font-size:12px}.footnote{font-size:8px}.send{width:31px;height:31px}.entry-tools button{font-size:10px}h1{font-size:27px;margin:16px 0 6px}#welcome p{font-size:12px}.suggestions{gap:8px;margin:18px 0 12px}.suggestions button{min-height:60px;padding:12px}.welcome-link{font-size:11px}.answer-label{font-size:9px}.understood{margin-bottom:7px}.understood span{font-size:8px}.understood p{font-size:10px}.message.user{max-height:48px;margin-bottom:9px}.bubble{font-size:11px;max-height:48px;padding:7px 11px}.value{font-size:27px}.answer-content>.matrix-scroll{max-height:75px}.explanation{margin-top:8px}.explanation-header{margin-bottom:6px}.solution-step strong,.solution-step p{font-size:11px}.step-number{width:21px;height:21px;line-height:21px;font-size:10px}.solution-step{gap:8px}.actions{gap:10px;margin-top:4px}.actions button{font-size:8px}.board-options{grid-template-columns:repeat(5,1fr);padding:9px;gap:4px}.board-options button{min-height:39px}.board-options button b{font-size:15px}.board-options button span{font-size:7px}.board-header{padding:9px 12px}.board-tabs button{padding:10px 4px}.avatar{width:23px;height:23px}.answer{gap:8px}}
@media(max-height:640px){body{grid-template-rows:48px minmax(0,1fr) auto}header{height:48px}.work-area{padding-top:8px}.symbol{width:33px;height:33px;font-size:26px}h1{margin:10px 0 4px;font-size:24px}#welcome p{margin:4px 0;font-size:11px}.suggestions{margin:12px 0 8px}.suggestions button{padding:9px;min-height:48px}.suggestions small{margin-top:3px}#composer{padding:7px 12px}#prompt{height:34px;min-height:34px}.composer-wrap{padding-top:4px;padding-bottom:6px}.footnote{margin-top:5px}.understood{display:none}.answer-label{margin-bottom:4px}.explanation{margin-top:5px}.board-options button{min-height:32px}.board-options button span{display:none}.board-options{padding:7px}.board-header{padding:6px 11px}.board-tabs button{padding:8px 3px}.grid-controls{margin:6px 0}.builder-heading{margin:5px 0}.editable-matrix input{padding:5px 3px}}
.work-area{height:100%;margin:0 auto;align-self:stretch;overflow:hidden}
#messages:empty{display:none}#welcome{margin:0 auto;flex:1;height:100%}#welcome>.symbol,#welcome>h1,#welcome>p,#welcome>.suggestions,#welcome>.welcome-link{flex-shrink:0}.work-area #board .board-options{grid-template-columns:repeat(5,1fr)}