CSS3中的鼠标悬停

Question

have this CSS3 code:

#box1
    {
    position: relative;
    width: 300px;
    border: 1px solid black;
    box-shadow:  -3px 8px 34px  #808080;
    border-radius: 20px;
    box-shadow: -8px 5px 5px #888888;
    right: 700px; 
    top:  -200px;
    height:  150px;
}


@-webkit-keyframes myfirst {
    0%   { right:700px; top:-200px;background: yellow;}
    50%  {background:blue; right:700px; top:200px;}
    100% { right:700px; top:-200px; background: yellow}
}

#stam {
    font-size: large;
    background: green;
    width: 100px;
    top: 400px;
    position: absolute;
}

#stam:hover ~ #box1 { -webkit-animation:myfirst 2s; }

you can see how the code works here: http://jsfiddle.net/FLe4g/2/

my question is: how can I do the animation so when I put the mouse on "stam" div the animation will stop on "50%" ( 50% {background:blue; right:700px; top:200px;}) of the animation, and only when I move the mouse from "stam" div, the animation continue? I'm really prefer that the solution will be with CSS3 and not with js... thank you!

Answer 1

For backward animation i used transition, so when you going forward you use animation frames and when you go backward you use transition:

#box1
    {
    position: relative;
    width: 300px;
    border: 1px solid black;
    box-shadow:  -3px 8px 34px  #808080;
    border-radius: 20px;
    box-shadow: -8px 5px 5px #888888;
    right: 300px; 
    top:  -200px;
    height:  150px;
    -webkit-transition: all 2s;
}


@-webkit-keyframes myfirst {
    0%   { right:300px; top:-200px;background: yellow;}
    100%  {background:blue; right:500px; top:200px;}
}

#stam {
    font-size: large;
    background: green;
    width: 100px;
    top: 400px;
    position: absolute;
}

#stam:hover ~ #box1 { 
    -webkit-transition: all 0s;
    background:blue; right:500px; top:200px;
    -webkit-animation:myfirst 2s; 
    -webkit-animation-fill-mode: forwards; 
    }​