.calculator{width:250px;margin:0 auto;padding:20px;border:1px solid #ccc;border-radius:5px;background-color:#f9f9f9}.display{width:calc(100% - 10px);margin-bottom:10px;padding:10px;font-size:20px}.buttons{display:grid;grid-template-columns:repeat(4,1fr);grid-gap:5px}.buttons button{padding:10px;font-size:18px;border:none;border-radius:5px;background-color:#fff;cursor:pointer}.buttons button:hover{background-color:#e0e0e0}