There are instructions... in the manual booklet. I never put in game tutorials as I personally can't stand them. Modern games I feel have a lot of hand holding so I try to avoid that.
The AI isnt buggy. It's behaving exactly as coded. As Saxmachine mentions the GB can't move things off-screen, so the enemy only become active once they enter the frame buffer (ie; just off screen). The double back was accidental but it gives the enemy random movement, which is what I wanted to begin with.
I'm glad you liked it enough to complete it, that says a lot.