body{
    margin: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background: #9ef7f6;
    background: linear-gradient(180deg, rgba(158, 247, 246, 1) 0%, rgba(158, 247, 246, 0.45) 50%, rgba(158, 247, 246, 0.17) 100%);
}
#calculator{
    font-family: Arial, sans-serif;
    background-color: hsla(177, 100%, 93%, 0.938);
    border-radius: 15px;
    max-width: 500px;
    overflow: hidden;
}
#display{
    width: 100%;
    padding: 20px;
    font-size: 5rem;
    text-align: left;
    border: none;
    background-color: hsla(176, 100%, 57%, 0.566);
}
#keys{
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
    padding: 25px;
}
button{
    width: 77px;
    height: 77px;
    border-radius: 50px;
    border: none;
    background-color: hsla(176, 100%, 50%, 0.247);
    color: rgba(0, 0, 0, 0.687);
    font-size: 3rem;
    font-weight: bold;
    cursor: pointer;
}
button:hover{
    background-color: hsla(176, 100%, 30%, 0.247);
}
button:active{
    background-color: hsla(176, 100%, 70%, 0.247);
}
.operator-btn{
    background-color: hsl(176, 100%, 50%);
}
.operator-btn:active{
    background-color: hsl(176, 100%, 40%);
}