Alright this game was not too bad. At first, I was very confused as to why I need to press the space bar to do a double jump after jumping once with the up arrow key. Once I figured out that the space bar functionality changes with each cartridge that I got, It made a lot more since since the space bar is actually the action button. I actually like how it changes between parts of the game because it helps to give each part of the game a distinct feel.
I did notice some odd things about the overall design. For instance, when I was dashing while running, I noticed that the character moved a bit even though I stopped, which lead to multiple instances where I almost fell off the platform. Perhaps you should modify that function so that the player stops completely once they stop moving after a dash. I was also a bit confused by how the level swapping worked after I got the first key, although it didn't take me too long to figure out how it all work and by extension, how to beat the second level. You should also make it a bit more clear the order in which the player needs to move after the first key to avoid confusion, such as adding a number by each cartridge that you collect. On the bright side, I didn't encounter any mechanical issues with either the portal or gravity flip level.
I also loved how the color of the whole room changed depending on which mechanic you had enabled, as it helped to further solidify each of them in addition to helping me figure out the order to beat level two. The sound effects were also implemented well, although I cannot say the same for the music. I think the track is just too short and loops too frequently. Perhaps if you made the track a bit longer, or had the music change based on which mechanic you had enabled, it would improve that aspect of the game immensely.
Overall, this game did a pretty decent job of not only tying into the theme, but also being a fun little experience. While there were a few issues that I encountered along the way, I believe that if you continued working on this game after the jam ends, I think it could be really great. Good job!