This one's too tough for me! I completed the first two levels, and I was able to get to the end of the third... the controls aren't tight enough to avoid the spikes, even when I know they're there. I tried placing a box in the way to help, and that still wasn't enough. Those spikes are out for blood! Similarly, I understood what to do in the fourth stage, and again despite knowing where the spikes are and what's expected of me, I lack the finesse to get through the obstacles. I promise I tried my best!
There is some flicking between the sprites which is noticeable while playing as the blue character. You should be able to easily fix that by adding the tiles to a sprite atlas.