Vault of Peril

Yes, the projectiles/spells are 3D shapes with only one face visible, else they wouldn't appear at the proper angle. Sprites can only face the floor.

I know VoP has a wall stick issue (but at least one of the very earliest FPSes did too) but I've since found a fairly easy way to get wall sliding working. I don't exactly understand how to implement what you're suggesting, but trying to work through it led me to the solution I'll use in my next game, so thanks!