2D Platformer Tutorial | Super Space-Stronaut

[ Planned Modifications ]

I'm thinking 3 worlds, each one has you collect one of 3 crystals at the end of a series of levels. Each world has levels with varying themes, challenges, and difficulties. 

Each time the player completes a world, you go back to a hub area that shows your progress (progress = how many of the three crystals you have).

You beat the game by beating each of the 3 worlds.