body{
    padding: 0;
    margin: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background: #C4DFAA;
}

/* container section */

.container{
    width: 45%;
    height: 45vh;
    padding: 10px;
    border-radius: 10px;
    box-shadow: 15px 15px 20px #90C8AC, 
                -15px -15px 20px #FFF;
}

/* display section */

.display #screen{
    width: 97%;
    height: 70px;
    font-size: 35px;
    outline: none;
    border: none;
    text-align: right;
    background: #ffffff;
    border-radius: 10px;
    box-shadow: inset 8px 8px 8px #CEE5D0,
                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: 90px;
    height: 30px;
    font-size: 16px;
    border: none;
    outline: none;
    margin: 5px;
    border-radius: 4px;
    box-shadow: 5px 5px 8px #00000020,
                -5px -5px 8px #ffffff;
                transition: .1s;
}

.btns .row button:hover {
    box-shadow: inset 5px 5px 8px rgba(16, 16, 16, 0.1),
                inset -5px -5px 8px #90C8AC;
                background: #90C8AC;
}

#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;
}

#ce {
    background: #FF3399;
    color: #FFF;
}

#ce:hover {
    box-shadow: inset 5px 5px 8px #E60073,
                inset -5px -5px 8px #FF3399;
}

#ac {
    background: #33CC33;
    color: #FFF;
}

#ac:hover {
    box-shadow: inset 5px 5px 8px #2Eb82E,
                inset -5px -5px 8px #33CC33;
}

@media (max-width: 1200px) {

    .btns{
        width: 100%;
        margin-top: 1.7em;
        margin-left: 2.5rem;
        display: flex;
        justify-content: center;
        align-items: center;
        flex-direction: column;
    }

    .btns .row button{
        width: 100px;
        height: 16px;
        font-size: 12px;
        border: none;
        outline: none;
        
    }
}

@media (max-width: 550px) {

    .btns{
        width: 100%;
        margin-top: 1.7em;
        margin-left: .5rem;
        display: flex;
        justify-content: center;
        align-items: center;
        flex-direction: column;
    }

    .btns .row button{
        width: 60px;
        height: 16px;
        font-size: 12px;
        border: none;
        outline: none;
        
    }
}

@media (max-width: 440px) {

    .btns{
        width: 100%;
        margin-top: 1rem;
        margin-left: .55rem;
        display: flex;
        justify-content: center;
        align-items: center;
        flex-direction: column;
    }

    .btns .row button{
        width: 40px;
        height: 12px;
        font-size: 10px;
        border: none;
        outline: none;
        
    }
}