style.css

/*-------------- RESET STYLE ------------------ */
html, body, div, span, applet, object, iframe,
h1, h2, h3, h4, h5, h6, p, blockquote, pre,
a, abbr, acronym, address, big, cite, code,
del, dfn, em, font, img, ins, kbd, q, s, samp,
small, strike, strong, sub, sup, tt, var,
b, u, i, center,
dl, dt, dd, ol, ul, li,
fieldset, form, label, legend,
table, caption, tbody, tfoot, thead, tr, th, td {
    margin: 0;
    padding: 0;
    border: 0;
    outline: 0;
    background: transparent;
    font-weight: bold;
}

input, select, option, textarea {
}

ol, ul {
    list-style: none;
}

a {
    text-decoration: none;
}
/*-------------- RESET STYLE ------------------ */

body {
    background-color: #2298DA;
}

div.main {
    width: 355px;
    margin: 50px auto;
    overflow: hidden;
    height: 485px;
}
#clear{
    position:relative;
}

div.input {
    width: 100%;
}

    div.input h1 {
        margin-right:10px;
        text-align:right;
        font-size: 65px;
        color: #fff;
        line-height: 77px;
    }

    div.input div {
        text-align: right;
        width: 340px;
        height: 60px;
        border-radius: 10px;
        background-color: #83B1C2;
        border: none;
        font-size: 30px;
        padding-right: 10px;
        padding-top: 15px;
    }

div.input_in {
    margin-top: 15px;
    width: 372px;
}

    div.input_in button {
        text-align: center;
        margin-bottom: 15px;
        margin-right: 13px;
        width: 75px;
        height: 50px;
        background-color: #546EA6;
        font-size: 24px;
        border: none;
        border-radius: 10px;
        box-shadow: 0px 5px #5877bb;
    }

    div.input_in .operator {
        background-color: #7c8cb0;
        box-shadow: 0px 5px #98a5c3;
    }

    div.input_in button:hover {
        color: #fff;
        background-color: #735ebb;
        box-shadow: none;
    }

    div.input_in .operator:hover {
        color: #fff;
        background-color: #8599c6;
    }

    div .input_in .equal {
        width: 258px;
        text-align: center;
        height: 50px;
        background-color: #D86441;
        font-size: 24px;
        border: none;
        border-radius: 10px;
        box-shadow: 0px 5px #ed714b;
    }

        div.input_in .equal:hover {
            background-color: #e28c72;
            box-shadow: none;
        }