:root{--bg: #0e0b16;--panel: #1c1626;--line: #342a45;--ink: #f1ecf7;--dim: #a597b8;--accent: #8455c0;--accent2: #b48ee8;--good: #6ee0a0;--bad: #ff8aa0}*{box-sizing:border-box}html,body{margin:0;height:100%}body{background:radial-gradient(900px 560px at 50% -8%,#221a33,var(--bg));color:var(--ink);font-family:system-ui,-apple-system,Segoe UI,sans-serif;display:flex;justify-content:center;-webkit-user-select:none;user-select:none}#app{width:100%;max-width:560px;padding:12px 12px 26px}header{text-align:center;margin-bottom:6px}h1{margin:0;font-size:30px;letter-spacing:7px;font-weight:800;color:var(--accent2)}.sub{margin:4px 0 0;color:var(--dim);font-size:13px}.bar{display:flex;gap:8px;justify-content:center;flex-wrap:wrap;align-items:center;margin:9px 0}.seg{display:inline-flex;background:var(--panel);border:1px solid var(--line);border-radius:999px;overflow:hidden}.seg button{background:none;border:none;color:var(--dim);padding:6px 14px;font:600 13px system-ui;cursor:pointer}.seg button.active{background:var(--accent);color:#fff}.btn{background:var(--panel);border:1px solid var(--line);color:var(--ink);padding:7px 16px;border-radius:999px;font:700 13px system-ui;cursor:pointer}.btn:hover{border-color:var(--accent2)}.btn.primary{background:var(--accent);color:#fff;border-color:var(--accent)}.scoreboard{display:flex;gap:10px;justify-content:center;margin:10px 0}.readout{background:#14101d;border:1px solid var(--line);border-radius:8px;padding:5px 16px;font:800 18px ui-monospace,monospace;color:var(--accent2);min-width:92px;text-align:center}.readout span{color:var(--dim);font-size:11px;display:block;font-weight:600;letter-spacing:.5px}.stage{position:relative;margin-top:6px}.board{background:linear-gradient(180deg,#1d1729,#16111f);border:1px solid var(--line);border-radius:14px;padding:30px 18px;min-height:180px;display:flex;flex-direction:column;align-items:center;justify-content:center;gap:22px}.exprline{display:flex;flex-wrap:wrap;gap:8px;justify-content:center;align-items:center}.tok{font:800 clamp(22px,8vw,40px) ui-monospace,"SF Mono",monospace;line-height:1;padding:6px 4px;border-radius:8px}.tok.num{color:var(--ink)}.tok.paren{color:var(--dim)}.tok.op{color:var(--dim);cursor:pointer;padding:6px 10px;border:2px solid transparent;transition:transform .08s,background .12s,color .12s}.tok.op:hover{color:var(--ink);background:#2a2138}.tok.op.legal{color:var(--accent2);background:#2c2140;border-color:var(--accent);box-shadow:0 0 0 0 var(--accent);animation:pulse 1.6s ease-in-out infinite}.tok.op.legal:hover{background:var(--accent);color:#fff}.tok.op.wrong{color:#fff;background:#7a2438;border-color:var(--bad);animation:shake .35s}@keyframes pulse{0%,to{box-shadow:0 0 #8455c08c}50%{box-shadow:0 0 0 5px #8455c000}}@keyframes shake{0%,to{transform:translate(0)}25%{transform:translate(-4px)}75%{transform:translate(4px)}}.prompt{margin:0;color:var(--dim);font-size:14px;text-align:center;min-height:18px}.prompt .good{color:var(--good)}.prompt .bad{color:var(--bad)}.overlay{position:absolute;inset:0;display:flex;align-items:center;justify-content:center;background:#0a0710cc;border-radius:14px;backdrop-filter:blur(3px)}.overlay.hidden{display:none}.card{background:var(--panel);border:1px solid var(--line);border-radius:16px;padding:22px 28px;text-align:center;max-width:320px}.card h2{margin:0 0 8px;font-size:24px;color:var(--accent2)}.card p{margin:6px 0;color:var(--dim);font-size:14px;line-height:1.7}.card p b{color:var(--ink)}.card .row{display:flex;gap:8px;justify-content:center;margin-top:16px}.hint{text-align:center;color:var(--dim);font-size:12px;margin-top:16px;line-height:1.6}.hint b{color:var(--accent2)}