如何在CSS3动画期间将div隐藏在另一个下方

Question

The CSS code :

.mainDiv{
    width: 600px;
    height: 600px;
    background-color: blue;
}

.innerDiv{
    width: 400px;
    margin: auto;
    height: 400px;
    background-color: green;
}

.innerDiv div{
    width: 50px;
    height: 50px;
    background-color: red;
    display: inline-block;
}


.removing{
    -webkit-animation: slideout 1s;
    animation: slideout 1s;
}

@-webkit-keyframes slideout {
    0% {
        -webkit-transform: translateX(0px);
        transform: translateX(0px);
    }
    100% {
        -webkit-transform: translateX(-200%);
        transform: translateX(-200%);
    }
}

@keyframes slideout {
    0% {
        -webkit-transform: translateX(0px);
        transform: translateX(0px);
    }
    100% {
        -webkit-transform: translateX(-200%);
        transform: translateX(-200%);
    }
}

Here is a jsFiddle of the problem.

What i would like it to do is this :

When the first red block moves outside of the green block, i would like it to be behind the blue block instead of in front of it.

Answer 1

add the line: overflow:hidden; to your .innerDiv css rule

Answer 2

Use z-index .

Example:

#somethingBehind {
    z-index: 1;
}

#somethingAtTheFront {
    z-index: 2;
}