I really like this idea! The graphics look really nice too, especially the crystals! I think it was a little too hard for me, even on Normal mode, the amount of crystals that swarm you was a bit overwhelming. It might be more balanced with a shorter delay between placing platforms? That way I could block off the crystals and then keep making platforms for myself too. It might also be good to start the player off a bit slower with less crystal enemies and wait to introduce the shooting one to help ease the player into the game more.
But I really like the concept! I hope you continue this project in the future, I see a lot of potential. Congrats!