Maybe there could be some kind of red effect only on the borders of the screen that would indicate the effect of the powerup so that the rest of the screen still remains normal.
At some point I increased the fov to 110 and it felt good playing so I stuck with it to this day but don't ask me when I started using it and which game I was playing back then. It's been too long to remember. #OldFart
That Zortch-o-pedia looks nice already. Looking forward to seeing it added to the game in the future.
Btw I had another brain fart when it comes to the level transition from a boss room to the start of the next episode. How about in the boss room there is some kind of teleporter or slipgate (Quake/Startgate reference maybe?) which you use as the exit and then at the start of each new episode there is a teleporter or slipgate through which you enter the new level. That way you don't really need much explanation how you ended up in this new area.