I like it! It's pretty cute and fun.
The stock piano music is cutesy at best, outright tedious at worst, especially since it's so short and repetitive (I do find it cool that the music changes instruments and tone between the two worlds). The pixel graphics, on the other hand, are pretty cute and nice, I like this style.
This game has a pretty interesting concept, giving its unique twist to the "double world" puzzle platforming idea. The opposite worlds (happiness and anger) are just a single fall away from each other (that might also work as a metaphor for bipolarity, but who knows), and sometimes, you have to use gravity to your advantage in order to hop on certain platforms, which would involve falling in one world in high speed so you can gain momentum by dropping into it and returning in full speed to the former world in order to reach a platform. These mechanics of gravitation around the line are very well explored in the stage design, which is nice. The hardcore stages feature crates to push around, and in general stages that are a lot more challenging than the regular stages, which are pretty cool.
The story told in the game is probably very relatable to many people, and to me as well. It doesn't try to be too introspective or disturbing, and instead remains a pretty simple, direct and comprehensible narrative/dissertation on how bipolarity works. It didn't change my life, but it was sure interesting.
One annoying thing is that the jumping controls sometimes catch me off guard, since you press up to jump in the happy world, and down to jump in the angry world. I also encountered a bug (actually, just a phenomenon resulting from the way physics works in this game) where I enter the angry world with too little momentum, and I end up orbiting the separation line very closely, which is especially annoying when there's no line-adjacent platform to land on. Also, sometimes (very rarely, thankfully) you'll be entering one of the worlds at high speeds without being able to see what's right above the character, and if that ends up being a spike, it's pretty annoying.
I'm going to greenlight this, in hopes that its flaws are ironed out and the end result is great.