An action packed beginning to start the game of! Really nice to force you to know how to switch before you can start the game. The player now knows which button is the main mechanic of the game.
I do have to say I was a bit panicked at the start not really knowing what everything does. Just being shot at had me panicking and trying to fumble myself through the first stage. I did like this though, just straight into the action.
The second level has some buttons that spawn enemies. This level teaches you that the gun guys can be killed by the switch and the slimes cannot. Really liked this as an introduction to this main mechanic, although having some indication of where an enemy will spawn would help.
The one level where you have to race the slime was a fun idea!
The latter half of the game turned into what I only could describe as "The Worlds Hardest Game" (Not literally like it was hard, but a game that has that specific name. look it up if you want to). This part had a different playstyle and I did like this more. Had you thinking about when to switch with all these spike balls coming at you. The last level also had a branching path, which is a cool design choice!
If I can be a little rude, the cow noise was starting to wear me down (I cant imagine what playtesting was like). Maybe make it a bit less loud and you could also make the pitches differ everytime to get a mario coin like effect. It was really funny to hear the cow moo every time though.
All in all, short and sweet game that showcases a lot of different mechanics.