This is a good start. For your modifications:
Your modifications are too small to earn full credit. All three of your levels are far to similar to each other and the changes you have made take very little time to do.
I suggest you take a look at the example 2D shooter modifications video to get an idea of what significant modifications look like:
Optional: 2D Shoot Modification Examples - SS21-CAS-117-730 - Games and Interactivity (msu.edu