:root{--ac:#0f766e;--ac2:#14b8a6;--acl:#ccfbf1;--bd:#d7dde3;--tx:#1f2937;--mut:#64748b;--ink:#0f172a;--rail:#f4f7f9}
*{box-sizing:border-box}
html,body{margin:0;height:100%;overflow:hidden;font-family:"Segoe UI",system-ui,sans-serif;color:var(--tx);background:#fff;user-select:none;-webkit-user-select:none}
body{display:flex;flex-direction:column}
/* thanh trên: tối, gọn */
#bar{display:flex;align-items:center;padding:0 10px;gap:2px;background:var(--ink);color:#e2e8f0;flex:none;height:46px;position:relative;z-index:20}
#ttl{flex:1;text-align:center;font-size:14px;color:#cbd5e1;white-space:nowrap;overflow:hidden;text-overflow:ellipsis;padding:0 10px;min-width:0}
.vsp{width:1px;height:20px;background:#334155;margin:0 6px}
.b{width:36px;height:36px;border:0;background:transparent;border-radius:9px;display:inline-flex;align-items:center;justify-content:center;cursor:pointer;color:#e2e8f0;flex:none;position:relative;padding:0}
.b:hover{background:rgba(255,255,255,.12)}
.b:disabled{opacity:.3;cursor:default}
.b.hid{display:none}
svg.ic{width:22px;height:22px;stroke-width:1.7;stroke-linecap:round;stroke-linejoin:round;fill:none;stroke:currentColor}
svg.ic .s{fill:none;stroke:currentColor}
svg.ic .f{fill:var(--icf,rgba(20,184,166,.28));stroke:none}
#info{display:inline-flex;align-items:center;gap:4px;margin:0 8px;font-size:13.5px;flex:none;color:#e2e8f0}
#info span{cursor:pointer;padding:4px 8px;border-radius:7px;background:rgba(255,255,255,.08)}
#info span:hover{background:rgba(255,255,255,.18)}
/* thanh công cụ dọc bên trái */
#rail{width:148px;flex:none;background:var(--rail);border-right:1px solid var(--bd);overflow-y:auto;overflow-x:hidden;padding:6px 8px 10px;z-index:15}
#rail .rg{margin-bottom:6px}
#rail .rt{font-size:10.5px;letter-spacing:.07em;text-transform:uppercase;color:var(--mut);padding:6px 2px 4px;font-weight:600}
#rail .rb{display:grid;grid-template-columns:1fr 1fr;gap:5px}
.tl{position:relative;height:56px;border:1px solid transparent;border-radius:12px;background:#fff;color:var(--tx);cursor:pointer;display:flex;flex-direction:column;align-items:center;justify-content:center;gap:2px;font:inherit;font-size:11.5px;padding:3px 2px;box-shadow:0 1px 2px rgba(15,23,42,.08)}
.tl:hover{border-color:var(--ac2);background:#f0fdfa}
.tl.on{background:var(--ac);color:#fff;border-color:var(--ac);--icf:rgba(255,255,255,.3)}
.tl.hid{display:none}
.tl svg.ic{width:24px;height:24px}
.tl .car{position:absolute;right:3px;top:3px;width:10px;height:10px;fill:none;stroke:currentColor;stroke-width:2.4;opacity:.6}
.tl span{line-height:1.05;white-space:nowrap}
.grp{display:flex;align-items:center;flex-wrap:wrap;gap:3px;padding:6px 6px;border-radius:12px;background:#fff;margin-bottom:5px;box-shadow:0 1px 2px rgba(15,23,42,.08)}
.dot{width:25px;height:25px;border-radius:50%;border:2px solid #fff;box-shadow:0 0 0 1px rgba(0,0,0,.2);cursor:pointer;position:relative;flex:none;margin:2px 3px;padding:0}
.dot.on{box-shadow:0 0 0 2.5px var(--ac)}
.szb{width:32px;height:30px;border:0;background:transparent;border-radius:8px;display:inline-flex;align-items:center;justify-content:center;cursor:pointer;flex:none}
.szb i{display:block;border-radius:50%;background:#334155}
.szb.on{background:var(--acl);box-shadow:0 0 0 1.5px var(--ac) inset}
.sep{width:1px;height:26px;background:var(--bd);margin:0 5px;flex:none}
@media (max-width:760px){#rail{width:100px;padding:4px}#rail .rb{grid-template-columns:1fr}#ttl{display:none}}
#main{flex:1;display:flex;min-height:0;position:relative}
#side{width:0;overflow:hidden;background:#f3f4f7;border-right:1px solid var(--bd);transition:width .15s;flex:none;position:relative}
#side.open{width:150px}
#side .inner{width:150px;height:100%;overflow-y:auto;padding:8px}
.thumb{margin-bottom:10px;cursor:pointer;text-align:center;font-size:12px;color:#555}
.thumb canvas{width:100%;display:block;border:2px solid transparent;border-radius:3px;box-shadow:0 1px 4px rgba(0,0,0,.25);background:#fff}
.thumb.on canvas{border-color:var(--ac)}
.thumb .tb{display:none;justify-content:center;gap:4px;margin-top:3px}
.thumb.on .tb{display:flex}
.thumb .tb button{border:1px solid #ccc;background:#fff;border-radius:6px;cursor:pointer;padding:1px 7px;font-size:13px}
#stage{flex:1;position:relative;overflow:hidden;background:#e7e9ee;min-width:0}
#c{position:absolute;inset:0;touch-action:none;display:block}
#hint{position:absolute;left:50%;top:8px;transform:translateX(-50%);background:rgba(30,30,40,.82);color:#fff;font-size:13px;padding:5px 14px;border-radius:16px;pointer-events:none;z-index:6;display:none;max-width:90%;text-align:center}
#ctx{position:absolute;display:none;background:#fff;border-radius:12px;box-shadow:0 4px 22px rgba(0,0,0,.22);padding:5px 7px;align-items:center;gap:1px;font-size:13.5px;white-space:nowrap;z-index:8;max-width:96%;flex-wrap:wrap}
#ctx button,#ctx select{border:0;background:transparent;padding:6px 8px;border-radius:8px;cursor:pointer;font:inherit;color:#222;display:inline-flex;align-items:center;gap:4px}
#ctx button:hover{background:#f1f2f5}
#ctx button.on{background:#d9f3ef;color:var(--ac);font-weight:600}
#ctx .lb{color:var(--mut);font-size:12.5px;padding:0 3px 0 5px}
#ctx .vs{width:1px;height:22px;background:#e5e7eb;margin:0 4px}
#ctx input{width:62px;font:inherit;padding:4px 6px;border:1px solid #cfd3da;border-radius:6px}
#sheets{height:36px;background:#f6f6f8;border-top:1px solid var(--bd);display:flex;align-items:flex-end;padding:0 8px;gap:2px;flex:none}
#sheets.hid{display:none}
.tab{padding:5px 14px;font-size:13px;background:#eceef2;border:1px solid var(--bd);border-bottom:0;border-radius:8px 8px 0 0;cursor:pointer}
.tab.on{background:#fff;font-weight:600;height:30px}
#addtab{border:0;background:transparent;font-size:20px;cursor:pointer;padding:0 12px;height:28px;color:#555}
#pop{position:fixed;display:none;background:#fff;border-radius:12px;box-shadow:0 4px 24px rgba(0,0,0,.25);padding:8px;z-index:60;min-width:170px;max-height:80vh;overflow:auto}
#pop .it{padding:7px 12px;border-radius:7px;cursor:pointer;font-size:14px;white-space:nowrap;display:flex;align-items:center;gap:8px}
#pop .it:hover{background:#f1f2f5}
#pop .it.on{color:var(--ac);font-weight:600}
#pop .gt{font-size:12px;color:var(--mut);padding:6px 12px 2px;text-transform:uppercase;letter-spacing:.03em}
#pop hr{border:0;border-top:1px solid #eee;margin:4px 0}
#pop .row{display:flex;align-items:center;gap:8px;padding:5px 8px;font-size:13.5px}
#pop .pens{display:flex;gap:4px;padding:4px}
#pop .pens button{width:40px;height:40px;border:1px solid #ddd;border-radius:9px;background:#fff;cursor:pointer;font-size:11px;padding:0}
#pop .pens button.on{background:var(--ac);color:#fff;border-color:var(--ac)}
#pop .pal{display:grid;grid-template-columns:repeat(10,24px);gap:5px;padding:6px}
#pop .pal i{width:24px;height:24px;border-radius:50%;cursor:pointer;display:block;border:1px solid rgba(0,0,0,.12)}
#pop .pal i.on{box-shadow:0 0 0 2px #fff,0 0 0 4px var(--ac)}
#pop canvas{display:block;margin:4px auto;border:1px solid #eee;border-radius:8px}
#pop input[type=range]{width:180px}
#pop .num{border:1px solid #ccc;border-radius:5px;background:#fff;width:24px;height:22px;cursor:pointer;padding:0}
#modal{position:fixed;inset:0;background:rgba(0,0,0,.38);display:none;align-items:center;justify-content:center;z-index:70}
#modal .box{background:#fff;border-radius:14px;padding:18px 22px;width:min(560px,94vw);max-height:92vh;overflow:auto;box-shadow:0 10px 40px rgba(0,0,0,.3);user-select:text}
#modal .box.wide{width:min(760px,96vw)}
#modal h3{margin:0 0 10px;font-size:18px}
#modal h4{margin:14px 0 4px;font-size:14px;color:var(--ac)}
#modal label{display:block;font-size:13px;color:var(--mut);margin:8px 0 3px}
#modal label.ck{display:flex;align-items:center;gap:7px;color:var(--tx);margin:5px 0}
#modal input[type=text],#modal input:not([type]),#modal input[type=number],#modal textarea,#modal select{width:100%;font:inherit;font-size:14.5px;padding:7px 9px;border:1px solid #cfd3da;border-radius:8px;background:#fff}
#modal .row{display:flex;gap:8px;align-items:flex-end;margin:3px 0}#modal .row>div{flex:1}
#modal .hint{font-size:12px;color:var(--mut);margin-top:8px;line-height:1.45}
#modal .act{display:flex;justify-content:flex-end;gap:8px;margin-top:16px}
#modal .act button,#modal .mini{font:inherit;padding:7px 16px;border-radius:9px;border:1px solid #cfd3da;background:#fff;cursor:pointer}
#modal .mini{padding:4px 10px;font-size:13px}
#modal .act button.ok{background:var(--ac);color:#fff;border-color:var(--ac)}
#modal .frow{display:flex;gap:6px;align-items:center;margin:4px 0}
#modal .frow input[type=text]{flex:1}
#modal .sw{width:26px;height:26px;border-radius:6px;border:1px solid #bbb;cursor:pointer;flex:none}
#modal .lim{display:flex;gap:5px;margin:2px 0 6px 32px}
#modal .lim input{width:25%!important}
#modal canvas.pv{width:100%;border:1px solid #e3e5ea;border-radius:8px;background:#fff;display:block}
#modal .err{color:#c62828;font-size:12.5px;min-height:16px}
#modal table.g td{padding:2px}
#modal table.g input{width:70px!important;padding:3px 5px;font-size:13px}
#modal .lib{display:grid;grid-template-columns:repeat(auto-fill,minmax(140px,1fr));gap:10px;margin-top:10px}
#modal .lib .card{border:1px solid #ddd;border-radius:10px;padding:8px;cursor:pointer;font-size:13px}
#modal .lib .card:hover{border-color:var(--ac)}
#modal .lib .card img{width:100%;border-radius:4px;display:block;margin-bottom:5px;background:#f3f3f3;aspect-ratio:3/4;object-fit:cover}
#txt{position:absolute;display:none;z-index:7;border:1.5px dashed var(--ac);background:rgba(255,255,255,.9);resize:none;outline:0;padding:0;margin:0;overflow:hidden;white-space:pre;user-select:text}
#tbar{position:absolute;display:none;z-index:9;background:#fff;border-radius:10px;box-shadow:0 3px 16px rgba(0,0,0,.25);padding:4px 6px;gap:2px;align-items:center;font-size:13px;flex-wrap:wrap;max-width:96%}
#tbar button,#tbar select{border:0;background:transparent;border-radius:6px;padding:5px 8px;cursor:pointer;font:inherit}
#tbar button.on{background:#d9f3ef;color:var(--ac)}
#tbar input[type=number]{width:52px;padding:3px;border:1px solid #ccc;border-radius:5px}
#toast{position:fixed;left:50%;bottom:70px;transform:translateX(-50%);background:#222;color:#fff;padding:8px 16px;border-radius:20px;font-size:13px;opacity:0;transition:opacity .3s;pointer-events:none;z-index:90}
input[type=color]{width:26px;height:26px;border:0;padding:0;background:none;cursor:pointer;margin:0 3px}

#pop .bgg{display:grid;grid-template-columns:1fr 1fr;gap:8px;padding:4px 6px}
#pop .bgi{cursor:pointer;border:1px solid var(--bd);border-radius:10px;padding:5px;text-align:center;font-size:12px}
#pop .bgi:hover{border-color:var(--ac)}
#pop .bgi i{display:block;height:34px;border-radius:6px;border:1px solid rgba(0,0,0,.15);margin-bottom:4px}
.hover-hint{cursor:move}

#modal .chips{display:flex;flex-wrap:wrap;gap:6px;margin:4px 0}
#modal .chip{font:inherit;font-size:13.5px;padding:6px 12px;border-radius:18px;border:1.5px solid #cfd3da;background:#fff;cursor:pointer}
#modal .chip:hover{border-color:var(--ac2)}
#modal .chip.on{background:var(--ac);border-color:var(--ac);color:#fff}
/* phông chữ mẫu tập viết tiểu học (Playwrite Việt Nam, giấy phép SIL OFL — xem fonts/PlaywriteVN-OFL.txt) */
@font-face{font-family:"Playwrite VN";src:url("../fonts/PlaywriteVN.ttf") format("truetype");font-weight:100 400;font-display:swap}
/* ô nhập công thức (MathLive) */
#modal math-field.mfield{flex:1;min-width:120px;font-size:21px;padding:3px 8px;border:1px solid #c9ced6;border-radius:8px;background:#fff;color:#111;--caret-color:#0f766e;--selection-background-color:#cdeee9;--contains-highlight-background-color:transparent}
#modal math-field.mfield:focus-within{outline:2px solid #0f766e;outline-offset:0}
#modal math-field.mfield::part(menu-toggle){display:none}
#modal .mtog{min-width:34px;font-family:"Cambria Math","Times New Roman",serif}
#modal label+math-field.mfield,#modal .askf math-field.mfield{display:block;width:100%;box-sizing:border-box}
/* công cụ lớp học (classroom.js) */
.fbox{position:fixed;z-index:60;min-width:260px;background:#fff;border-radius:12px;box-shadow:0 10px 30px rgba(0,0,0,.25);font:14px "Segoe UI",sans-serif;color:#222;overflow:hidden}
.fbox .fh{display:flex;align-items:center;justify-content:space-between;padding:8px 10px 8px 14px;background:#0f766e;color:#fff;cursor:move;touch-action:none;user-select:none}
.fbox .fx,#w-curtain .fx,#w-spot .fx{border:0;background:rgba(255,255,255,.18);color:#fff;width:28px;height:28px;border-radius:7px;font-size:18px;cursor:pointer}
.fbox .fb{padding:10px 14px 14px}
.fbox .trow{display:flex;flex-wrap:wrap;gap:6px;align-items:center;margin:6px 0}
.fbox .trow button{padding:6px 12px;border:1px solid #cfd4dc;border-radius:8px;background:#f6f7f9;cursor:pointer;font:inherit}
.fbox .trow button.ok{background:#0f766e;color:#fff;border-color:#0f766e}
.fbox .tdig{font:700 64px/1.1 "Segoe UI",sans-serif;text-align:center;letter-spacing:2px;font-variant-numeric:tabular-nums;color:#0f172a;padding:4px 0}
.fbox.warn .tdig{color:#e65100}.fbox.end .tdig{color:#c62828;animation:tblink .6s steps(2) infinite}
.fbox.roll .tdig{color:#1f5f99}
@keyframes tblink{50%{opacity:.25}}
.fbox.big{left:50%!important;top:50%!important;transform:translate(-50%,-50%)}.fbox.big .tdig{font-size:min(28vw,220px)}
#w-curtain{position:fixed;z-index:55;background:repeating-linear-gradient(90deg,#2b3a55 0 26px,#24324b 26px 52px);box-shadow:0 6px 18px rgba(0,0,0,.35)}
#w-curtain .cgrip{position:absolute;left:50%;bottom:0;transform:translate(-50%,50%);background:#0f766e;color:#fff;padding:8px 18px;border-radius:20px;cursor:ns-resize;touch-action:none;user-select:none;font:600 14px "Segoe UI",sans-serif;box-shadow:0 3px 10px rgba(0,0,0,.3)}
#w-curtain .fx{position:absolute;right:10px;top:10px}
#w-spot{position:fixed;inset:0;z-index:58;pointer-events:none}
#w-spot .fx{position:absolute;right:14px;top:56px;pointer-events:auto}
#w-rec{position:fixed;z-index:61;left:50%;top:54px;transform:translateX(-50%);display:flex;gap:10px;align-items:center;background:#fff;border-radius:20px;padding:5px 6px 5px 14px;box-shadow:0 4px 14px rgba(0,0,0,.25);font:600 14px "Segoe UI",sans-serif}
#w-rec i{width:12px;height:12px;border-radius:50%;background:#e53935;animation:tblink 1s steps(2) infinite}
#w-rec button{border:0;background:#c62828;color:#fff;border-radius:14px;padding:5px 12px;cursor:pointer;font:inherit}