body{height:100vh;display:flex;justify-content:center;align-items:center;background-color:#f0f0f0}.calculator{width:320px;margin:0 auto;border:1px solid #ccc;border-radius:10px;padding:20px;box-shadow:0 4px 10px #0003;background-color:#fff}.display{height:60px;background-color:#f0f0f0;font-size:3rem;text-align:right;padding:10px;border-radius:5px;margin-bottom:10px}.buttons{display:grid;grid-template-columns:repeat(4,1fr);gap:10px}button{height:50px;border:none;border-radius:5px;background-color:#007bff;color:#fff;font-size:18px;cursor:pointer;transition:background-color .2s}button:hover{background-color:#0056b3}button:active{background-color:#004494}