body{
    margin: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background-color: rgb(0, 0, 0);
}

#calculator{
    font-family: Arial, sans-serif;
    background-color: rgb(28, 28, 28);
    border-radius: 15px;
    max-width: 500px;
    overflow: hidden;
}

#display{
    width: 100%;
    padding: 20px;
    color: white;
    font-size: 5rem;
    text-align: left;
    border: none;
    background-color: rgb(54, 54, 54);;
}

#keys{
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
    padding: 25px;
}

button{
    width: 100px;
    height: 100px;
    border-radius: 50px;
    border: none;
    color: white;
    font-size: 3rem;
    font-weight: bold;
    cursor: pointer;
    background-color: rgb(61, 62, 77);
}

button:hover{
    background-color: rgb(81, 82, 100);
}

button:active{
    background-color: rgb(73, 74, 83);
}

.operation-key{
    background-color: rgb(146, 63, 0);
}

.operation-key:hover{
    background-color: rgb(178, 79, 4);
}

.operation-key:active{
    background-color: rgb(178, 89, 20);
}