Good idea of switching between the characters and the two levels I've played were fun. It needs more polish though. For instance, it wasn't clear who needs to go to which cave. I mixed them up on the second level. I really liked the trick to switch when in mid-air creating a platform for the other guy. But it seemed like after you switch back your "platform" slime was instantly on the ground for some reason. Controls felt a bit too responsive. The art is simple but nice, slime animation is quite smooth. Audio could be developed more but it's really nice that you cared to include some soundtrack, it added to the mood. Overall, you have a good basic game there and you could definitely develop it into a really fun puzzle platformer. Good job!