Sorry for the late response Spark
-You can't damage the bosses before the battle starts anymore, which avoids the AI bug.
-Fixed the missing bullets when changing characters.
-Added midway checkpoints.
I'll take into account adding an intro, weapons/items/characters got screen and ending, I didn't consider it priority, but yeah, the feeling of accomplishment is lesser without them.
I'll see what I can do with the background issues you mentioned, I think adding a small optional customizable filter should remedy the issue a bit (Prob going to revise the colors later too, but it's not priority as of yet)
Thanks for the support! ^.^