.square_btn {
    position: relative;
    display: inline-block;
    padding: 0.25em 0.5em;
    text-decoration: none;
    color: #FFF;
    background: #fd9535;/*背景色*/
    border-bottom: solid 4px #d27d00;/*少し濃い目の色に*/
    border-radius: 6px;/*角の丸み*/
    box-shadow: inset 0 6px 0 rgba(255,255,255,0.2), 0 6px 6px rgba(0, 0, 0, 0.19);
    font-weight: bold;
}

.square_btn:active {
    border-bottom: solid 6px #fd9535;
    box-shadow: 0 0 6px rgba(0, 0, 0, 0.30);
}