Congrats on a very interesting unique game mechanic, I love building the level as you go. The visuals are great, and the sounds and atmosphere are good too.
Sadly I never got near completing the game as I really really struggled with the controls...If you'd presented me with this control scheme back in the PSX days, no problem, back then every game had a unique and idiosyncratic control scheme that had to be learnt, but with the standardization of control schemes in recent years that are now so instinctive and ingrained, i found it nearly impossible to maneuver as I wanted to the moment I was under any pressure. Also a bad run of luck saw me have an apprentice spawn in the 1st or 2nd room I nearly every game.
Beyond the controls (which may be more down to me than the controls themselves) I felt the UI was the only place the game was lacking. I picked up what I assumed were bullets and keys, but the inventory just showed some numbers next to different coloured squares, so I wasn't sure what I had in there.
But those 2 points aside, a very cool game, and a mechanic that I may well take inspiration from for a future prototype, and see what I come up with. Great Job!