Solid prototype. I really like the contrast of the 2d player sprite, and the 3d platforms. Gives the game a really unique feel that I think you could continue with as a deliberate design choice. The gameplay is obviously a prototype, but I think you should consider what kind of game you want to make. The button size changing could work very well for a puzzle game, but I'm not sure if that's the game you'd like to create. If you're set on leaning closer towards a platformer, try to think about how you can add more depths to the buttons. As of now you don't have to think much about using them because they're just in the path, but I think there are definitely some cool ways to make changing sizes an action that the player needs to think carefully about (maybe adding multiple paths that can only be traversed by certain sizes). Regardless, even just getting a game made in 2 days and posted is still super impressive! I hope you continue doing game dev, either with this concept, or trying something new!