Interesting idea! I also agree with the comments below that it felt like the switching didn't pull my character down as fast as I expected it to, resulting in me hitting spikes I don't think I should've hit.
It would also be interesting to see the brain grow bigger when they take on more brain cells (maybe this already happens but I'm so bad at the game I didn't see it lol). That would create a wrinkle with a risk/reward factor and make this a bit less generic in its gameplay. I just feel like it needs a little something to jazz it up, you know?