Fun idea! Makes me think about when I used to play fire boy and water girl :).
A couple suggestions: it'd be nice if there were checkpoints of sorts in that tutorial level (at any section where you can die) because it got a little frustrating when I kept dying at the dash jump and had to start the whole level over again :(. Secondly, the controls are a little awkward for Grump. Maybe you could use IJKL as a mirror to WASD instead of the arrow keys. That way you can have lets say F and E for Hap and H and U for Grump for their shoot and dash abilities to be a little easier to control.
Also here are some bugs I ran into while playing (in a 48-hour jam, there's bound to be some, don't worry :) ):
- The sign just after "Press F to Shoot" in the happy world also says "Press F to Shoot"
- The music track doesn't loop (which is sad cuz it's a really good one :( )
- Sometimes when you jump it's like you hit your head on a really short ceiling so you don't really jump. Couldn't really figure out what was causing it, but it was very prevalent when trying to jump up the stairs in the first platforming section.
- In the section that tutorializes dashing into enemies, you can actually dash through the little gap without having to break the enemies.
I'd love to see where you take this if you're planning to keep working on it. Congrats on the game!