The latest version includes many more sound effects, a better ending, and additional points when you stomp multiple enemies. World 1-1 should now be close to complete except for the small bonus room, which is my next project. I'm almost at 8K of assembly program (excluding graphics), and a have about 3K of the 32K left in total. I do wonder how they managed on a NES system with only 2K onboard RAM?
I noticed that sometimes fire Mario cannot hit any enemies with his fire balls. Please let me know if you can reproduce this issue.
Updates source code in post #1.