/**
 * @since 150527 21:16
 * @author vivaxy
 */
* {
    box-sizing: border-box;
}

body {
    margin: 0;
}

.box {
    width: 100px;
    height: 100px;
    padding: 10px;
}

.inner {
    border: 2px solid #eee;
    background-color: #fdf;
    width: 100%;
    height: 100%;
}