Hey, sorry for the somewhat late reply.
I don't really have a definite answer but I can say that almost every planned room exists in the game.
It is only version 1 of said rooms though which means a lot of them will be changed / are missing stuff.
But at least almost the entire game world is "done".
As for bosses, around 25% of them are done, so quite a bit left to do in this department.
Enemy types, can't really give any progress numbers here because this is not as planned out as the rest but I'm definitely not done with enemy types and more will be added.
Then there's the planned sound / music rework..
So.. there's still quite a bit to do as you can see.
There's been so many issues where I've had to rework parts of the game because the engine I use didn't play well with what I wanted to do and I'm hoping this particle stuff I've been working on (which is almost done now) is the last of these issues so I can get back to adding new content again. (namely continue working on bosses which was interrupted by the particle stuff)
Anyway, not sure what else to say, hopefully this gives you some answers.