Great game for one person !
It's fun and quite accessible, even my kids were able to play and liked it.
I love the aesthetics of playing on an old TV, with the scanlines effect on it. That blends in really well. Reminds me of my NES.
The characters are cute. Going cartoony for Halloween is refreshing.
There are some bugs, though : sometimes we're stuck after attacking, and if we switch in the middle of a platform, we can get stuck inside.
The jumps are really tight, especially those when we need to switch while jumping. Lower platforms at the beginning would have been easier to start with.
Other thing : I played perfectly with an X360 controller, but the layout is not perfect. Maybe the switch command on an R button would have been better.
And my computer's fans go crazy when the game runs ! Maybe because I run it under Linux with Wine but it's strange.
Overall a very pleasant piece of work. Good job !