:root{--paper:#eae8df;--ink:#212728;--muted:#747875;--line:#c9cbc4;--pale:#f5f4ee;--orange:#d74f31;--night:#253234;--mint:#bed1c2;--font:Arial,Helvetica,sans-serif;--mono:Consolas,'Courier New',monospace}
*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:var(--paper);color:var(--ink);font-family:var(--font);line-height:1.42}
button{font:inherit;cursor:pointer}button:disabled{opacity:.35;cursor:not-allowed}button:focus-visible,input:focus-visible{outline:3px solid var(--orange);outline-offset:3px}
.masthead{height:78px;border-bottom:1px solid var(--ink);display:flex;justify-content:space-between;align-items:center;padding:0 clamp(18px,4vw,70px)}
.brand{display:flex;align-items:center;gap:12px}.brand-mark{font:34px Georgia,serif;line-height:1;background:var(--night);color:var(--paper);width:52px;height:52px;display:grid;place-items:center}
.brand strong{font-size:17px;letter-spacing:.15em;display:block}.brand small{font:9px var(--mono);letter-spacing:.16em;color:var(--muted)}
.mast-right{font:10px var(--mono);letter-spacing:.08em;display:flex;align-items:center;gap:10px}.edition{border-left:1px solid var(--line);margin-left:16px;padding-left:20px;color:var(--muted)}
.live-led{display:inline-block;flex-shrink:0;height:7px;width:7px;border-radius:100%;background:var(--orange)}
main{max-width:1600px;margin:0 auto;padding:0 clamp(18px,4vw,70px)}.hero{padding:45px 0 38px}
.eyebrow,.hero-rule,.panel-index,.panel-hint,.under-note,.result-footer,.filters,.toolbar,.selected-root>span,.operators-label,.representation>span,.challenge-meta,.preset-row,.study-rail>span,.stage-visual>p{font:10px var(--mono);letter-spacing:.085em}
.eyebrow{display:flex;gap:22px;color:var(--muted)}.index{color:var(--orange)}
h1{font-size:clamp(59px,8vw,117px);line-height:.92;font-weight:500;letter-spacing:-.075em;margin:25px 0 25px}h1 em{color:var(--orange);font-weight:400}
.hero>p{font-size:18px;line-height:1.5;max-width:580px;margin:0 0 37px}.hero-rule{display:flex;justify-content:space-between;border-top:1px solid var(--ink);padding-top:12px;max-width:890px;gap:15px;color:var(--muted)}
.switcher{display:flex;border-bottom:1px solid var(--ink);gap:0}.mode{border:0;background:transparent;color:var(--muted);padding:17px clamp(12px,3.6vw,48px);font:12px var(--mono);letter-spacing:.1em;border-bottom:4px solid transparent}
.mode span{font-size:9px;margin-right:16px}.mode.active{color:var(--ink);border-bottom-color:var(--orange);background:var(--pale)}
.mode-panel{padding:30px 0 70px}.mode-panel[hidden]{display:none}.workspace,.compose-grid{display:grid;grid-template-columns:minmax(0,1.1fr) minmax(0,1fr);gap:clamp(24px,4vw,62px)}
.panel-heading{min-height:64px;display:flex;justify-content:space-between;align-items:start;gap:10px}.panel-index{color:var(--orange)}h2{font-size:25px;font-weight:500;letter-spacing:-.045em;margin:4px 0 0}.panel-hint{color:var(--muted);padding-top:6px;text-align:right}
.canvas-shell{height:465px;background:var(--pale);border:1px solid var(--ink);position:relative;overflow:hidden;touch-action:none}
#sketch{position:relative;z-index:2;width:100%;height:100%;display:block;touch-action:none;cursor:crosshair}
.axis-h,.axis-v{position:absolute;pointer-events:none;z-index:0}.axis-h{left:0;right:0;top:50%;border-top:1px dashed #e0dfd5}.axis-v{top:0;bottom:0;left:50%;border-left:1px dashed #e0dfd5}
.canvas-watermark{pointer-events:none;position:absolute;z-index:1;top:50%;left:50%;transform:translate(-50%,-50%);font:12px var(--mono);letter-spacing:.2em;color:#b9bbb4;white-space:nowrap}.canvas-watermark[hidden]{display:none}
.toolbar{display:flex;justify-content:space-between;align-items:center;padding:10px 0;border-bottom:1px solid var(--line)}
.tool-left,.tool-right{display:flex;gap:16px;align-items:center}.toolbtn,.minorbtn{background:none;border:0;padding:8px 0;font:11px var(--mono);letter-spacing:.04em;color:var(--ink)}.toolbtn:hover,.minorbtn:hover{color:var(--orange)}
input[type=range]{width:95px;accent-color:var(--orange)}.under-note{display:flex;align-items:center;gap:8px;color:var(--muted);margin-top:18px;line-height:1.65}
.filters{display:flex;gap:6px;flex-wrap:wrap;border-bottom:1px solid var(--line);padding:0 0 12px}.filter{font:10px var(--mono);background:transparent;border:1px solid var(--line);padding:9px 10px;color:var(--muted)}
.filter.selected{background:var(--ink);border-color:var(--ink);color:var(--paper)}
.result-grid{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:9px;margin:15px 0;min-height:350px;align-content:start}
.empty-results{grid-column:1/-1;display:grid;place-items:center;text-align:center;height:335px;border:1px dashed var(--line);color:var(--muted);font:13px var(--mono);padding:20px}
.result-item{border:1px solid var(--line);background:var(--pale);min-height:105px;padding:5px 4px 7px;display:flex;flex-direction:column;align-items:center;gap:2px;text-align:center;transition:background .12s,transform .12s}
.result-item:hover,.result-item:focus-visible{background:#dae3d9;transform:translateY(-2px)}.result-char{font:47px 'Segoe UI Symbol','Noto Sans Symbols 2','DejaVu Sans',serif;min-height:60px;line-height:1.25}
.result-name{max-width:100%;font:9px var(--mono);color:var(--muted);white-space:nowrap;overflow:hidden;text-overflow:ellipsis}.result-footer{display:flex;justify-content:space-between;color:var(--muted);border-top:1px solid var(--line);padding-top:13px;gap:10px}
.compose-grid{grid-template-columns:minmax(0,1.12fr) minmax(0,.88fr)}.stage-visual{height:310px;border:1px solid var(--ink);background:var(--night);color:#f5f3e9;display:flex;flex-direction:column;justify-content:center;align-items:center;position:relative}
.canonical-preview{width:100%;height:240px;display:grid;place-items:center}.canonical-preview svg{width:min(270px,80%);height:230px}
.stage-visual>p{position:absolute;bottom:12px;left:16px;color:#a6bdb2}.preset-row{display:flex;gap:8px;flex-wrap:wrap;align-items:center;margin:19px 0 27px}.preset-row>span{width:100%;color:var(--muted)}
.preset{background:transparent;border:1px solid var(--line);font:10px var(--mono);padding:9px 11px;letter-spacing:.03em}.preset:hover,.preset.on{border-color:var(--ink);background:var(--ink);color:var(--paper)}
.selected-root{border-top:1px solid var(--line);border-bottom:1px solid var(--line);padding:14px 0}.selected-root>span{color:var(--muted)}
.selected-root>div{display:flex;align-items:center;gap:14px}.current-base{font:56px 'Segoe UI Symbol','DejaVu Sans',serif}.selected-root>div>span:nth-child(2){font:11px var(--mono);color:var(--muted);margin-right:auto}
.operators-label{margin-top:22px;color:var(--muted)}.operators-label span{color:#959893}.operator-list{display:grid;grid-template-columns:repeat(5,minmax(0,1fr));gap:7px}
.operator{min-height:80px;border:1px solid var(--line);background:var(--pale);display:flex;flex-direction:column;align-items:center;justify-content:center;gap:5px}
.operator>span{font:39px 'Segoe UI Symbol','DejaVu Sans',serif;line-height:1}.operator>small{font:9px var(--mono);color:var(--muted)}
.operator.active{background:var(--night);color:white;border-color:var(--night)}.operator.active>small{color:var(--mint)}
.export-column{padding-left:0}.representation{padding:14px 0 13px;border-bottom:1px solid var(--line);display:grid;grid-template-columns:1fr auto;align-items:center}
.representation>span{grid-column:1/-1;color:var(--muted)}.symbol-output{font:37px 'Segoe UI Symbol','DejaVu Sans',serif;min-height:48px}
.representation-visual svg{width:130px;height:80px}.semantic-output{font-size:16px;padding:7px 0}.codepoints{font:10px var(--mono);color:var(--muted);grid-column:1/-1;margin:4px 0}
.representation button{background:transparent;border:1px solid var(--ink);color:var(--ink);font:9px var(--mono);padding:9px 10px}
.representation button:hover{background:var(--ink);color:white}.compat-note{font-size:12px;color:var(--muted);line-height:1.6;margin-top:19px}
.learn-layout{display:grid;grid-template-columns:minmax(0,1fr) 260px;gap:65px}.learn-intro{max-width:550px;color:var(--muted)}
.challenge-sign{display:grid;place-items:center;background:var(--night);height:315px;margin:25px 0 13px}.challenge-sign svg{height:260px;width:320px;max-width:90%}
.challenge-meta{display:flex;justify-content:space-between;color:var(--muted)}.challenge-choices{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:12px;margin:16px 0}
.choice{display:grid;place-items:center;background:var(--pale);border:1px solid var(--line);height:106px}.choice:hover{border-color:var(--orange)}.choice svg{height:70px;width:100%}
.choice:disabled{opacity:.45}.choice.correct{background:#d9e6d9;border-color:#5c8659;opacity:1}.choice.wrong{background:#f1d5d0;border-color:var(--orange);opacity:1}
.feedback{min-height:28px;font-size:13px;color:var(--ink)}.nextbtn{background:var(--orange);color:white;border:0;padding:12px 28px;font:12px var(--mono)}
.study-rail{border-top:1px solid var(--ink);padding-top:16px}.study-rail h3{font-size:30px;font-weight:500;line-height:1.07;letter-spacing:-.055em}.study-rail p{font-size:13px;line-height:1.7;color:var(--muted)}
.study-rail button{display:block;border-top:1px solid var(--line);width:100%;text-align:left}
footer{border-top:1px solid var(--ink);padding:22px 0 46px;display:flex;justify-content:space-between;gap:25px;font:10px var(--mono);color:var(--muted)}
footer>div{display:flex;flex-direction:column;gap:6px}footer strong{font-size:17px;letter-spacing:.1em;color:var(--ink)}footer p{max-width:330px;line-height:1.65}
@media(max-width:900px){.workspace,.compose-grid{grid-template-columns:1fr}.learn-layout{grid-template-columns:1fr;gap:30px}.canvas-shell{height:380px}.result-grid{grid-template-columns:repeat(6,1fr);min-height:230px}.stage-visual{height:280px}}
@media(max-width:580px){.masthead{height:66px}.brand-mark{height:42px;width:42px;font-size:27px}.brand strong{font-size:13px}.brand small{font-size:7px}.mast-right{font-size:8px}.edition{display:none}.hero{padding-top:28px}.hero-rule{font-size:8px}.hero-rule span:last-child{display:none}.mode{font-size:10px;flex:1;padding:13px 7px}.mode span{margin-right:5px}.panel-hint{font-size:8px}.canvas-shell{height:330px}.result-grid{grid-template-columns:repeat(4,1fr)}.result-item{min-height:96px}.result-char{font-size:42px}.operator-list{grid-template-columns:repeat(4,1fr)}.challenge-sign{height:260px}footer{flex-direction:column}}
@media(prefers-reduced-motion:reduce){*{scroll-behavior:auto!important;transition:none!important}}
/* FIELD-LAB ERGONOMICS v1: sketch reachable without initial scrolling on desktop. */
@media(min-width:901px){
.hero{display:grid;grid-template-columns:minmax(0,1.15fr) minmax(270px,.72fr);grid-template-areas:"eyebrow eyebrow" "headline summary" "rule rule";column-gap:34px;padding:25px 0 17px}
.hero .eyebrow{grid-area:eyebrow}
.hero h1{grid-area:headline;font-size:clamp(62px,6.4vw,92px);line-height:.90;margin:12px 0 15px}
.hero>p{grid-area:summary;font-size:16px;margin:0;align-self:center;max-width:430px}
.hero-rule{grid-area:rule;max-width:none;margin-top:7px}
.mode-panel{padding-top:18px}
}