:root{color:#18211f;background:#edf3f1;font-family:Inter,PingFang SC,Microsoft YaHei,Arial,sans-serif;font-synthesis:none;text-rendering:optimizeLegibility;-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale}*{box-sizing:border-box}body{min-width:320px;min-height:100vh;margin:0}button{font:inherit}.app-shell{min-height:100vh;display:grid;place-items:center;padding:28px;background:linear-gradient(90deg,rgb(20 74 67 / 5%) 1px,transparent 1px),linear-gradient(rgb(20 74 67 / 5%) 1px,transparent 1px),#edf3f1;background-size:32px 32px}.calculator{width:min(100%,620px);border:1px solid #b9cbc6;border-radius:8px;background:#fbfdfc;box-shadow:0 24px 70px #24423c29;padding:clamp(16px,3vw,24px)}.topbar{display:flex;align-items:center;justify-content:space-between;gap:16px;margin-bottom:16px}.eyebrow{margin:0 0 4px;color:#4d6a64;font-size:12px;font-weight:700;letter-spacing:0;text-transform:uppercase}h1{margin:0;color:#162320;font-size:clamp(24px,5vw,36px);line-height:1.08;letter-spacing:0}.mode-toggle{width:76px;height:44px;border:1px solid #96aaa5;border-radius:8px;background:#e6f0ed;color:#183831;font-weight:800;cursor:pointer}.screen{min-height:146px;display:grid;align-content:end;gap:8px;border:1px solid #aebfba;border-radius:8px;background:#15211f;padding:18px;color:#edf8f5;overflow:hidden}.expression,.result{width:100%;overflow-wrap:anywhere;text-align:right;letter-spacing:0}.expression{min-height:24px;color:#95aaa4;font-size:clamp(16px,3.5vw,20px);line-height:1.35}.result{min-height:50px;color:#fff;font-size:clamp(36px,8vw,58px);font-weight:800;line-height:1}.error{margin:0;color:#f4b6a2;font-size:14px;text-align:right}.status-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:10px;margin:14px 0}.status-grid div{min-width:0;border:1px solid #d3dfdc;border-radius:8px;background:#f4f8f7;padding:10px 12px}.status-grid span,.status-grid strong{display:block;min-width:0;overflow-wrap:anywhere}.status-grid span{color:#637570;font-size:12px}.status-grid strong{margin-top:4px;color:#1d332e;font-size:14px}.keypad{display:grid;grid-template-columns:repeat(5,minmax(0,1fr));gap:9px}.key{min-width:0;aspect-ratio:1.28;border:1px solid #c7d6d2;border-radius:8px;background:#fff;color:#172320;font-size:clamp(16px,3vw,21px);font-weight:750;letter-spacing:0;cursor:pointer;transition:transform .12s ease,border-color .12s ease,background-color .12s ease}.key:hover{border-color:#6f9188;background:#eef6f3}.key:active{transform:translateY(1px)}.key.utility{background:#e8efed;color:#243b36}.key.science{background:#edf5f2;color:#1d574d}.key.operator{background:#203a35;border-color:#203a35;color:#fff}.key.equals{background:#c65f3f;border-color:#c65f3f;color:#fff}.key.danger{background:#7e2d31;border-color:#7e2d31;color:#fff}.key.wide{grid-column:span 2;aspect-ratio:auto}@media(max-width:620px){.app-shell{padding:12px;align-items:start}.calculator{padding:14px}.status-grid{grid-template-columns:1fr}.keypad{gap:7px}.key{min-height:50px}}