(no z-index)
2
6
10
(no z-index)
4
8
12
(no z-index)
2
6
10
z-index: 5
4
8
12
z-index: 1;
2
6
10
z-index: 2;
4
8
12
z-index: 2;
2
6
10
z-index: 1;
4
8
12