*{box-sizing:border-box}body{margin:0;background:var(--cr-bg);color:var(--cr-text);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI","Microsoft YaHei",sans-serif}.practice-shell{max-width:960px;margin:auto;padding:24px 20px 40px}header,nav,.question-head,.actions{display:flex;align-items:center;gap:12px;flex-wrap:wrap}header{justify-content:space-between}a{color:#0071e3;text-decoration:none;padding:10px 0}nav a{padding:10px;border-radius:8px}nav a[aria-current=page]{background:rgba(0,113,227,.12);font-weight:700}.eyebrow{color:#0071e3;font-weight:700;margin:24px 0 6px}h1{font-size:26px;margin:0}h2{font-size:20px;line-height:1.5;margin:12px 0}.muted{color:var(--cr-text-muted);font-size:14px;line-height:1.65}.question-head{justify-content:space-between;color:var(--cr-text-muted);font-size:14px}#exercise,#finish,#loadError{background:var(--cr-bg-card);border:1px solid rgba(128,128,128,.24);border-radius:14px;padding:20px;margin-top:20px}.exercise-grid{display:grid;grid-template-columns:minmax(0,440px) minmax(0,1fr);gap:24px;align-items:start}.exercise-grid.no-board{grid-template-columns:1fr}#practiceBoard{width:100%;aspect-ratio:1;position:relative}.answer-panel{min-width:0}#options{display:grid;gap:10px}button{font:inherit;line-height:1.5;min-height:46px;padding:10px 16px;border:1px solid rgba(128,128,128,.35);border-radius:9px;background:var(--cr-bg);color:var(--cr-text);cursor:pointer}button:disabled{opacity:.5;cursor:default}button:focus-visible,a:focus-visible{outline:3px solid #0071e3;outline-offset:3px}button.option{text-align:left;width:100%;padding:14px}.option[aria-pressed=true]{border-color:#0071e3;background:rgba(0,113,227,.12);box-shadow:inset 0 0 0 1px #0071e3}.primary{background:#0071e3;color:white;border-color:#0071e3}.actions{margin-top:12px}.actions button{flex:1}#selected{min-height:24px;color:var(--cr-text-muted);font-size:14px}#requestError{color:#cf3434;line-height:1.5}#feedback{margin-top:18px;border-top:1px solid rgba(128,128,128,.24);padding-top:16px;line-height:1.65}#result{font-size:20px}#feedback[data-correct=true] #result{color:#168443}#feedback[data-correct=false] #result{color:#c05b18}[hidden]{display:none!important}@media(max-width:700px){.practice-shell{padding:16px 12px 32px}#exercise,#finish,#loadError{padding:14px}.exercise-grid{grid-template-columns:1fr;gap:16px}#boardWrap{max-width:min(100%,430px);width:100%;margin:auto}h1{font-size:23px}h2{font-size:18px}header{gap:4px}nav{gap:4px}}html[data-theme=dark] a,html[data-theme=dark] .eyebrow{color:#74b5ff}html[data-theme=dark] #feedback[data-correct=true] #result{color:#65d891}html[data-theme=dark] #feedback[data-correct=false] #result{color:#ffba7a}

.practice-shell nav{display:flex;align-items:center;gap:8px;min-width:0;max-width:100%;flex-wrap:wrap}.practice-shell nav label{font-size:13px}.practice-shell select{min-height:44px;max-width:100%;width:min(310px,100%);padding:8px;border:1px solid rgba(128,128,128,.35);border-radius:8px;background:var(--cr-bg);color:var(--cr-text);font:inherit}select:focus-visible{outline:3px solid #0071e3;outline-offset:3px}

.practice-shell .muted,.practice-shell .question-head,.practice-shell #selected{color:#596474}html[data-theme=dark] .practice-shell .muted,html[data-theme=dark] .practice-shell .question-head,html[data-theme=dark] .practice-shell #selected{color:#bac4d2}