:root{font-family:system-ui,Avenir,Helvetica,Arial,sans-serif;line-height:1.5;font-weight:400;color-scheme:light dark;color:#ffffffde;background-color:#000;font-synthesis:none;text-rendering:optimizeLegibility;-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale}body{margin:0;padding:0;overflow:hidden}*{margin:0;padding:0;box-sizing:border-box}body{font-family:-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,Oxygen,Ubuntu,Cantarell,sans-serif;display:flex;justify-content:center;align-items:center;min-height:100vh;background:linear-gradient(135deg,#667eea,#764ba2)}.calculator{background:#2d3748;border-radius:20px;box-shadow:0 20px 60px #0000004d;padding:20px;width:320px}.display{background:#1a202c;color:#fff;font-size:2.5rem;padding:20px;text-align:right;border-radius:10px;margin-bottom:20px;min-height:80px;display:flex;align-items:center;justify-content:flex-end;word-wrap:break-word;word-break:break-all;font-weight:300}.buttons{display:grid;grid-template-columns:repeat(4,1fr);gap:10px}.btn{background:#4a5568;color:#fff;border:none;border-radius:10px;padding:20px;font-size:1.5rem;cursor:pointer;transition:all .2s;font-weight:500}.btn:hover{background:#5a6578;transform:translateY(-2px)}.btn:active{transform:translateY(0)}.btn.operator{background:#ed8936}.btn.operator:hover{background:#f6ad55}.btn.clear{background:#fc8181;grid-column:span 1}.btn.clear:hover{background:#feb2b2}.btn.equals{background:#48bb78;grid-column:4;grid-row:5 / 7}.btn.equals:hover{background:#68d391}.btn.zero{grid-column:span 2}.btn.plus{grid-row:3 / 5}