:root{color:#172026;font-synthesis:none;text-rendering:optimizelegibility;-webkit-font-smoothing:antialiased;--surface:#fff;--surface-muted:#e8eef0;--surface-raised:#edf2f4;--ink:#172026;--ink-muted:#5b6870;--number:#f8fafb;--function:#e6f0ec;--function-hover:#d9e7e1;--operator:#0f5d6b;--operator-hover:#0b4c58;--equals:#bd4f19;--equals-hover:#9c4115;--danger:#b42318;--focus:#2d6cdf;--border:#d7e0e3;--display-surface:#10242b;--display-ink:#fff;--display-muted:#b8c8ce;--display-error:#ffcbc5;--shadow:0 18px 45px #17202624;background:#f4f7f8;font-family:Inter,ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,Segoe UI,sans-serif}*{box-sizing:border-box}body{min-width:320px;min-height:100vh;margin:0}body,button{font:inherit}#app{place-items:center;min-height:100vh;padding:24px;display:grid}.calculator{border:1px solid var(--border);background:var(--surface);width:min(100%,380px);box-shadow:var(--shadow);border-radius:8px;padding:18px}.calculator[data-theme=dark]{--surface:#16242a;--surface-muted:#263941;--surface-raised:#203239;--ink:#f5fafb;--ink-muted:#b4c2c8;--number:#1f3037;--function:#213b37;--function-hover:#2b4a44;--operator:#24a0b7;--operator-hover:#1a879c;--equals:#e06b2c;--equals-hover:#bf551d;--danger:#ff8f83;--focus:#8ab4ff;--border:#395159;--display-surface:#0b161a;--display-ink:#fff;--display-muted:#9fb5bd;--display-error:#ffc2ba;--shadow:0 18px 45px #00000047}.calculator-toolbar{justify-content:space-between;align-items:center;gap:12px;margin-bottom:14px;display:flex}.calculator-toolbar h1{color:var(--ink);margin:0;font-size:1rem;font-weight:800}.theme-toggle{border:1px solid var(--border);background:var(--surface-raised);min-width:72px;min-height:38px;color:var(--ink);cursor:pointer;touch-action:manipulation;border-radius:8px;font-size:.95rem;font-weight:800;transition:background .14s,border-color .14s,color .14s,transform 80ms}.theme-toggle:hover{background:var(--surface-muted)}.theme-toggle:active{transform:translateY(1px)}.theme-toggle:focus-visible{outline:3px solid var(--focus);outline-offset:2px}.display-shell{background:var(--display-surface);min-height:132px;color:var(--display-ink);border-radius:8px;align-content:end;gap:8px;margin-bottom:14px;padding:18px;display:grid}.display{width:100%;min-height:52px;color:var(--display-ink);text-align:right;text-overflow:ellipsis;white-space:nowrap;font-size:clamp(2rem,10vw,3rem);font-weight:700;line-height:1.08;overflow:hidden}.expression{min-height:20px;color:var(--display-muted);text-align:right;font-size:.95rem}.error-message{min-height:20px;color:var(--display-error);text-align:right;margin:0;font-size:.95rem}.keypad{grid-template-columns:repeat(4,minmax(0,1fr));gap:10px;display:grid}.key{border:1px solid var(--border);background:var(--number);min-height:58px;color:var(--ink);cursor:pointer;touch-action:manipulation;border-radius:8px;font-size:1.2rem;font-weight:700;transition:background .14s,border-color .14s,color .14s,transform 80ms}.key:hover{background:var(--surface-muted)}.key:active{transform:translateY(1px)}.key:focus-visible{outline:3px solid var(--focus);outline-offset:2px}.key.utility{background:var(--surface-raised);color:var(--ink-muted)}.key.function{background:var(--function);color:var(--ink)}.key.function:hover{background:var(--function-hover)}.key.operator{border-color:var(--operator);background:var(--operator);color:#fff}.key.operator:hover{background:var(--operator-hover)}.key.equals{border-color:var(--equals);background:var(--equals);color:#fff;grid-row:span 2}.key.equals:hover{background:var(--equals-hover)}.key.wide{grid-column:span 2}.has-error .display{color:var(--display-error)}@media (width<=420px){#app{align-items:stretch;padding:12px}.calculator{align-self:center;padding:14px}.calculator-toolbar{margin-bottom:12px}.display-shell{min-height:118px;padding:14px}.keypad{gap:8px}.key{min-height:54px;padding-inline:6px;font-size:1.08rem}}