I'm glad you enjoyed it! As far as the limitation goes, it definitely ended up becoming less of the core mechanic as the development progressed. I'm not entirely sure I understand what you mean about avoiding the mirror pieces though?
Basically the way the bomb placement (and thus the theme implementation) works is that every cycle, a new clone copies your movement of the previous frame, and periodically drops bombs. Originally you were actually able to directly see the enemies, however later on in development (upon adding the mirror background) I made it so that you could only see the clones in the reflection. As far as showing the player how the game works this is probably not super good to be honest, but during playtesting I found that the enemies ended up being more distracting than helpful. I think that if I moved forwards with this project, I might honestly scrap large parts of that aspect and focus more on the bullet grazing as the core mechanic. Anyhow, hopefully this gives you some more insight to the implementation of the limitation (although it's admittedly a bit weak haha)
Viewing post in From the Looking Glass jam comments
I mean I saw my reflections when I stepped over the mirror shards so I figured that by avoiding them, there wouldn't be any reflections of mine to place bombs, but to my disappointment, the bombs appeared regardless of where I was, and also, the bombs appeared even where there weren't any shards.
Yes, it would have been quite a mess with all of the player trails being visible, especially in a bullet hell, so it was a wise decision to make them only barely visible in the shards. I think the reflections look really good, though; layer masks are quite an advanced thing so I'm impressed you got that to work.