calculator.css

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

body{
    min-height: 100vh; /**/
    background: #efeff2;
    display: flex;
    justify-content: center;
    align-items: center;
}

.calcul{
    width: 300px;
    height: 550px;
    box-shadow: 4px 4px 30px rgba(0,0,0,0.3);
    border: 1px solid #fff;
    border-radius: 12px;
    background-color: #22252D;
    overflow: hidden; /**/
}

form input{
    width : 100%;
    height: 150px;
    border : 1px solid #fff;
    border-radius: 12px;
    font-size: 2rem;
    padding: 1rem;
    color: #fff;
    background: #000;
    text-align: right;
    pointer-events: none; /**/
}


.buttons{
    display: flex;
    flex-wrap: wrap; /**/
    justify-content: space-between;
    padding: 20px;
}

button{
    flex: 0 0 22%; /**/
    margin: 5px 0;
    width: 60px;
    height: 52px;
    font-size: 22px;
    font-weight: 600;
    border: 1px solid #fff;
    border-radius: 50px;
    cursor: pointer; /**/
}

.btn-yellow{
    background: grey;
    color: #fff;
}

.btn-yellow:hover{
    background-color: #fff;
    color: #000;
}

.btn-grey{
    background: rgb(224, 224, 224);
}

.btn-grey:hover{
    background-color: grey;
    color: #fff;
}

.btn-equal{
    background: blue;
    color: #fff;
}


.btn-clear{
    background: grey;
    color: #fff;
}

.op{
    background: grey;
    color: #fff;
}

.op:hover{
    background-color: #fff;
    color: #000;;
}

.op-3:hover{
    background-color: #fff;
    color: #000;
}