body{
    padding: 0;
    margin: 0;
    display: flex;
    justify-content: center;/*horizantal middle*/
    align-items: center;/*vartical middle*/
    min-height: 100vh;
    background: #ecf0f3;
}

.container{
    padding: 10px;
    border-radius: 8px;
    box-shadow: 12px 12px 20px #cbced1,
                   -12px -12px 20px #ffffff;
}

.display #screen{
    width: 97%;
    height: 70px;
    font-size: 35px;
    outline: none;
    border: none;
    text-align: right;/*start right*/
    padding-right: .5em;
    background: #ecf0f3;
    border-radius: 6px;
    box-shadow: inset 8px 8px 8px #cbced1,
                inset -8px -8px 8px #ffffff;
}

.btns{
    width: 100%;
    margin-top: 1.7em;
    display: flex;
    justify-content: center;
    align-items: center;
    flex-direction: column;
}

.btns .row button{
    width: 58px;
    height: 30px;
    font-size: 16px;
    border: none;
    outline: none;
    margin: 5px;
    border-radius: 4px;
    box-shadow:  5px 5px 8px #00000020,
                 -5px -5px 8px #ffffff;
}

.row button:hover {
    box-shadow: inset 5px 5px 8px rgba(16, 16, 16, .1),
        inset -5px -5px 8px #fff;
    background: #fff;
}

.display #screen {
    margin-bottom: .5em;
    height: 70px;
    font-size: 35px;
    outline: none;
    border: none;
    text-align: right;
    padding-right: .5em;
    background: #ecf0f3;
    border-radius: 6px;
    box-shadow: inset 8px 8px 8px #cbced1,
        inset -8px -8px 8px #ffffff;
}

#eval {
    background: #33ccff;
    color: #fff;
    box-shadow: inset 5px 5px 8px #66d9ff,
        inset -5px -5px 8px #00ace6;
}

#eval:hover {
    box-shadow: inset 5px 5px 8px #00ace6,
        inset -5px -5px 8px #00ace6;
}

#ac {
    background: #33cc33;
    color: #fff;
}

#ac:hover {
    box-shadow: inset 5px 5px 8px #2eb82e,
        inset -5px -5px 8px #33cc33;
}

#ce {
    background: #ff3399;
    color: #fff;
}

#ce:hover {
    box-shadow: inset 5px 5px 8px #e60073,
        inset -5px -5px 8px #ff3399;
}