使用 CSS 禁用动画效果

我正在为我的网站制作一个滑出式菜单。

单击菜单图标时，我想禁用菜单向上动画的方式，并使其保持静态。我该怎么做？

http://jsfiddle.net/3w539Lct/

我相信答案在我的CSS中，但到目前为止，试错失败了：

html, 
body, 
.container, 
.content-wrap {
    overflow: hidden;
    width: 100%;
    height: 100%;
}
.container {
    background: #373a47;
}
.menu-wrap a {
    color: #b8b7ad;
}
.menu-wrap a:hover,
.menu-wrap a:focus {
    color: #c94e50;
}
.content-wrap {
    overflow-y: scroll;
    -webkit-overflow-scrolling: touch;
}
.content {
    position: relative;
    background: #b4bad2;
}
.content::before {
    position: absolute;
    top: 0;
    left: 0;
    z-index: 10;
    width: 100%;
    height: 100%;
    background: rgba(0,0,0,0.3);
    content: '';
    opacity: 0;
    -webkit-transform: translate3d(100%,0,0);
    transform: translate3d(100%,0,0);
    -webkit-transition: opacity 0.4s, -webkit-transform 0s 0.4s;
    transition: opacity 0.4s, transform 0s 0.4s;
    -webkit-transition-timing-function: cubic-bezier(0.7,0,0.3,1);
    transition-timing-function: cubic-bezier(0.7,0,0.3,1);
}
/* Menu Button */
.menu-button {
    position: fixed;
    z-index: 1000;
    margin: 1em;
    padding: 0;
    width: 2.5em;
    height: 2.25em;
    border: none;
    text-indent: 2.5em;
    font-size: 1.5em;
    color: transparent;
    background: transparent;
}
.menu-button::before {
    position: absolute;
    top: 0.5em;
    right: 0.5em;
    bottom: 0.5em;
    left: 0.5em;
    background: linear-gradient(#373a47 20%, transparent 20%, transparent 40%, #373a47 40%, #373a47 60%, transparent 60%, transparent 80%, #373a47 80%);
    content: '';
}
.menu-button:hover {
    opacity: 0.6;
}
/* Close Button */
.close-button {
    width: 1em;
    height: 1em;
    position: absolute;
    right: 1em;
    top: 1em;
    overflow: hidden;
    text-indent: 1em;
    font-size: 0.75em;
    border: none;
    background: transparent;
    color: transparent;
}
.close-button::before,
.close-button::after {
    content: '';
    position: absolute;
    width: 3px;
    height: 100%;
    top: 0;
    left: 50%;
    background: #bdc3c7;
}
.close-button::before {
    -webkit-transform: rotate(45deg);
    transform: rotate(45deg);
}
.close-button::after {
    -webkit-transform: rotate(-45deg);
    transform: rotate(-45deg);
}
/* Menu */
.menu-wrap {
    position: absolute;
    z-index: 1001;
    width: 300px;
    height: 100%;
    background: #373a47;
    padding: 2.5em 1.5em 0;
    font-size: 1.15em;
    -webkit-transform: translate3d(-320px,0,0);
    transform: translate3d(-320px,0,0);
    -webkit-transition: -webkit-transform 0.4s;
    transition: transform 0.4s;
    -webkit-transition-timing-function: cubic-bezier(0.7,0,0.3,1);
    transition-timing-function: cubic-bezier(0.7,0,0.3,1);
}
.menu, 
.icon-list {
    height: 100%;
}
.icon-list {
    -webkit-transform: translate3d(0,100%,0);
    transform: translate3d(0,100%,0);
}
.icon-list a {
    display: block;
    padding: 0.8em;
    -webkit-transform: translate3d(0,500px,0);
    transform: translate3d(0,500px,0);
}
.icon-list,
.icon-list a {
    -webkit-transition: -webkit-transform 0s 0.4s;
    transition: transform 0s 0.4s;
    -webkit-transition-timing-function: cubic-bezier(0.7,0,0.3,1);
    transition-timing-function: cubic-bezier(0.7,0,0.3,1);
}
.icon-list a:nth-child(2) {
    -webkit-transform: translate3d(0,1000px,0);
    transform: translate3d(0,1000px,0);
}
.icon-list a:nth-child(3) {
    -webkit-transform: translate3d(0,1500px,0);
    transform: translate3d(0,1500px,0);
}
.icon-list a:nth-child(4) {
    -webkit-transform: translate3d(0,2000px,0);
    transform: translate3d(0,2000px,0);
}
.icon-list a:nth-child(5) {
    -webkit-transform: translate3d(0,2500px,0);
    transform: translate3d(0,2500px,0);
}
.icon-list a:nth-child(6) {
    -webkit-transform: translate3d(0,3000px,0);
    transform: translate3d(0,3000px,0);
}
.icon-list a span {
    margin-left: 10px;
    font-weight: 700;
}
/* Shown menu */
.show-menu .menu-wrap {
    -webkit-transform: translate3d(0,0,0);
    transform: translate3d(0,0,0);
    -webkit-transition: -webkit-transform 0.8s;
    transition: transform 0.8s;
    -webkit-transition-timing-function: cubic-bezier(0.7,0,0.3,1);
    transition-timing-function: cubic-bezier(0.7,0,0.3,1);
}
.show-menu .icon-list,
.show-menu .icon-list a {
    -webkit-transform: translate3d(0,0,0);
    transform: translate3d(0,0,0);
    -webkit-transition: -webkit-transform 0.8s;
    transition: transform 0.8s;
    -webkit-transition-timing-function: cubic-bezier(0.7,0,0.3,1);
    transition-timing-function: cubic-bezier(0.7,0,0.3,1);
}
.show-menu .icon-list a {
    -webkit-transition-duration: 0.9s;
    transition-duration: 0.9s;
}
.show-menu .content::before {
    opacity: 1;
    -webkit-transition: opacity 0.8s;
    transition: opacity 0.8s;
    -webkit-transition-timing-function: cubic-bezier(0.7,0,0.3,1);
    transition-timing-function: cubic-bezier(0.7,0,0.3,1);
    -webkit-transform: translate3d(0,0,0);
    transform: translate3d(0,0,0);
}