I didn't read the description at first, so I thought that snakes just go invisible from time to time :D
It feels good to play, even though you don't control shooting, as everything happens in a nice rythm, great work with that!
Art looks great and the variety of enemies is nice. Those crabs are scary :)
I wasn't sure what was the end goal in each level, as at first I was waiting for timer to go to 0, but then I realized that the gray wall is not colliding with player and you can just walk through it and reach level end. I suppose this is a bug.