style.css

#controls.hide {
    opacity: 0;
}

.btn {
    border: 0 none;
    height: 30px;
    padding: 0;
    width: 30px;
    background-color: transparent;
    display: inline-block;
    margin: 7px 5px 0;
    vertical-align: top;
    opacity: 0.6;
    cursor: pointer;
    color: #fff;
    fill: currentColor;
}

.btn:hover {
    opacity: 0.9;
}

.btn.disabled {
    opacity: 0.2;
}

#btnPage {
    color: white;
    font-family: Arial, sans-serif;
    width: 40px;
    opacity: 0.8;
}

.page {
    box-shadow: 1px 1px 4px rgba(0, 0, 0, 0.3);
}

#controls {
    background: rgba(50, 50, 50, 0.9) none repeat scroll 0 0;
    height: 44px;
    line-height: 44px;
    position: fixed;
    text-align: center;
    bottom: 50px;
    transition: 0.3s ease 0s;
    width: 230px;
    left: 50%;
    margin-left: -115px;
    box-shadow: 1px 1px 4px rgba(0, 0, 0, 0.5);
    border-radius: 2px;
}
#controls-left {
    display: inline-block;
    left: 0;
    position: absolute;
}
#controls-center {
    display: inline-block;
}
#controls-right {
    display: inline-block;
    right: 0;
    position: absolute;
    line-height: 34px;
}

#idrviewer {
    bottom: 0;
    left: 0;
    right: 0;
    position: absolute;
    top: 0;
    background: #666 none repeat scroll 0 0;
}