2D Shooter

These modifications sound good, what specifically are you planning on modifying on each one?

1. As a tip, when making new levels, try to make sure that they're significant and unique/different from others in some shape or form. Adding new enemy types, challenges, or obstacles can help with this!
2. How will your levels tie together in a logical progression?
3. With adding visual assets, this is a great opportunity to learn a new skill or practice an existing one. I'd highly recommend that the art you add is custom-made, it'll look a lot more unique and be a more significant change.