* {
    padding: 0px;
    margin: 0px;
    font-family: Arial, Microsoft JhengHei;
}

.container {
    width: 600px;
    height: 600px;
    margin: 50px auto;
    border-radius: 50px;
    background-color: #c4e1e1;
}

.container input[type="text"] {
    width: 500px;
    height: 40px;
    margin: 45px;
    padding: 5px;
    border: none;
    border-radius: 20px;
    box-shadow: -3px -3px 0px #CCC;
    font-size: 30px;
    color: #444;
}

hr {
    width: 90%;
    height: 3px;
    margin: 0px 5% 30px 5%;
    border: none;
    background-color: #FFF;
}

.row {
    width: 500px;
    margin: 0px auto;
}

.container input[type="button"] {
    width: 20%;
    height: 50px;
    margin: 15px 2%;
    border: none;
    font-size: 24px;
    color: #444;
    line-height: 50px;
    border-radius: 20px;
    text-align: center;
    outline: 0;
    cursor: pointer;
}

.num {
    background-color: #FFF;
}

.sign {
    background-color: #ffe153;
}

.clear {
    background-color: #c2ff68
}

.sum {
    background-color: #ffad86;
}

@media screen and (max-width:768px) {
    .container {
        width: 500px;
        margin: 0px auto;
    }
    .container input[type="text"] {
        width: 400px;
    }
    .row {
        width: 400px;
    }
}

@media screen and (max-width:500px) {
    .container {
        width: 400px;
    }
    .container input[type="text"] {
        width: 300px;
    }
    .row {
        width: 300px;
    }
    .container input[type="button"] {
        width: 21%;
        margin: 15px 1%;
    }
}

@media screen and (max-width:400px) {
    .container {
        width: 360px;
    }
    .container input[type="text"] {
        width: 260px;
    }
    .row {
        width: 260px;
    }
    .container input[type="button"] {
        width: 23%;
        margin: 15px 0px;
    }
}