style.css

*{
    margin: 0;
    padding: 0;
    font-size: 18px;
    box-sizing: border-box;

}
body{
    display: flex;
    height: 100vh;
    justify-content: center;
    align-items: center;
}
.container{
    display: block;
    width: 320px;
    background-color: antiquewhite;
    border: 1px solid #333;
}

.answer{
    border: none;
    width: 100%;
    height: 5rem;
    background-color: #333;
    color: #d7ff5f;
    font-size: 60px;
    padding: 0 10px;
    box-sizing: border-box;
}
.clear, .equal{
    width: 160px;
    background-color: #585858;
    cursor: pointer;
}
.clear:hover, .equal:hover{
    background-color: blueviolet;
}
.clear:active, .equal:active{
    background-color: darkmagenta;
}
.buttons{
    width: 80px;
    cursor: pointer;

}
.buttons:hover{
    background-color: #ddd;
}
.buttons:active{
    background-color: #bbb;
}
input{
    margin-right: -5px;
    height: 50px;
    border: 1px solid #333;
}