Really nice; at first I thought this would be a very easy game, but it's a lot more trying than it seems once the gray tiles start moving :)
The only thing that I would improve, is the feedback on a correct entry; the first three times, I actually thought I'd made a mistake because the left guy lost a life. Improving the feedback here to make it more clear that you were correct would have been nice.
Added it to my list of 'favorite games I've played tonight'!
One last note: I really liked the game page with the GIF's; was very well done!