body{
height:100vh;
display:flex;
justify-content:center;
align-items:center;
background:linear-gradient(135deg,#1f4037,#99f2c8);
font-family:Arial;
}

.calculator{
background:#222;
padding:20px;
border-radius:15px;
box-shadow:0 10px 30px rgba(0,0,0,0.4);
width:300px;
}

#display{
width:100%;
height:50px;
font-size:22px;
text-align:right;
padding:10px;
border:none;
margin-bottom:15px;
border-radius:8px;
}

.buttons{
display:grid;
grid-template-columns:repeat(4,1fr);
gap:10px;
}

button{
padding:15px;
font-size:18px;
border:none;
border-radius:8px;
background:#333;
color:white;
cursor:pointer;
transition:0.2s;
}

button:hover{
background:#00c9ff;
color:black;
}

.equal{
background:#ff9800;
color:white;
}

.equal:hover{
background:#ffa726;
}

.zero{
grid-column:span 2;
}