* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
background-color: #1e1e1e;
min-height: 100vh;

display: flex;
justify-content: center;
align-items: center;

font-family: Arial, sans-serif;

}

.calculator {
background-color: #2d2d2d;
padding: 20px;
border-radius: 12px;
width: 320px;
}

.display {
background-color: #111;
color: white;

overflow-x: auto;
white-space: nowrap;

padding: 20px;
margin-bottom: 15px;

text-align: right;
font-size: 2rem;

border-radius: 8px;

}

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

button {
padding: 20px;

border: none;
border-radius: 8px;

background-color: #444;
color: white;

font-size: 1.2rem;

cursor: pointer;

}

button:hover {
background-color: #555;
}

.zero {
grid-column: span 4;
}