Got two easy gfx bug fixes yesterday, both related to background drawing:

* Fixed background breakable objects in 64th Street, it was caused by missing writes to a VRAM mirror.

* Fixed castle tiles not properly drawn in Sexy Parodius stage 3B (a.k.a. Castlevania / Akumajou stage). It probably need a blending effect for the mosaic windows tho:

Added dual screen support for Run N Gun: they used a multiplexer mechanism that sends signals at alternating intervals to each screen. What wasn’t obvious since now is that connected VRAMs were also bankswitched, and that was causing issues even in single screen mode because the supposedly unused sprite RAM is in reality used for internal gameplay state.