Glad you liked it! Unfortunately, I don't plan on making this game too feature rich, at best I might add 2 more enemies, but don't keep your hopes up for that. Stage rework is in the works, as I'm fully aware how much stage 2 sucks (check the credits button, btw)
As for when R5 will arrive, I can't tell, since I work on this game as a hobby and learning experience; I also have my day job and social life, so free time devoted to this might not come often.