body {
    background-color: #F8F8F8;
    font-family: Verdana, serif;
    font-size: 14px;
    font-weight: normal;
    margin: 15px;
}

#calculator_container {
    width: 400px;
    height: 605px;
    margin: 0 auto;
    border: 1px solid #ccc;
    background-color: #fff;
}

#calculator_screen {
    width: 90%;
    height: 80px;
    margin: 4% auto;
    padding: 0 1%;
    background: #A1A1A1;
    border: 2px #222 solid;
    color: white;
    font-size: 55px;
    line-height: 80px;
    text-align: right;
}

.line {
    width: 100%;
    height: 2px;
    background-color: #ccc;
}
#title {
    float: left;
    width: 36%;
    margin: 3.2% 6.8%;
    font-size: 12px;
    font-weight: bold;
}
.button-row {
    width: 95%;
    height: 70px;
    margin: 0 auto;
    text-align: center;
    line-height: 70px;
}
.button {
    float: left;
    margin: 3.2%;
    width: 18%;
    height: 100%;
    background: #c3c3c3;
    color: white;
    cursor: pointer;
    font-size: 44px;
    border: 1px #CCC solid;
}
.button:hover {
    background: #00b2ee;
}
.button.empty {
    background: inherit;
    cursor: inherit;
    border: 1px white solid;
}
.button.red {
    background-color: red;
}
.button.red:hover {
    background-color: #A62A2A;
}

.operation.selected {
    background-color: #00b2ee;
}