Interacting with the mouse


On my banner i’m working on i have this animated reatating balls in the background. I wanna make it so that when the cursor is at the left side of it the frames of the image go in reverse and at the right side they play normal.
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And…if you could, could it reverse on the last frame it played on at the right side when you move to the left?

I hope this isn’t too hard to explain to me.