To answer your previous comment, there is no way to add or edit a level when in game, but it is possible to put your own and compile again the ROM.
I can provide source code, but be aware that some tools are "internal" and made for myself or using other softwares (see README), so it might be hard to understand and apply the complete workflow (you can ask if you have any issue). In particular, the level editor is made in Python but does not handle everything (see HOWTO in the folder). Have fun!
https://drive.google.com/file/d/1y1E8rPyCdC6FpVFRsKW6oWOen7WhJbuo