Oh to get to the boss you have to go to the middle room and then you'll notice an entry point at the top. You have to defeat all three enemies and corrupt all three rooms though.
Sorry about the unpredictable aspect of the game, I just wanted it to be challenging. Especially for the left room use the walls. I'll try and make the game less difficult maybe by showing a portion of the path the enemy is following.
And being shot a couple of times.. Yeah that was my mistake because enemies were shooting in the background on other rooms. I thought I coded something to stop the bullets but I guess that didn't work. I'll test more later.
And thanks for your feedback :)