This game is really uncomfortable to play. Especially character's motion and sliding are too annoying, and I fell off a platform many times. This slippery mechanic would suit more with the game that has big area. But this game needs to be more like Super Mario Bros or some 2D platformer games.
And there is no music or any sound effects, but you claim that you have created the vast majority of the music.
But the building feature in this game is a little surprising.
Overall, the game is not good. I hope this can improve your next project or this project if you want to still work on it.