Game Boy / Super Game Boy:

New mapper support

M161 mapper — adds support for the Mani 4-in-1 multicart (a forged-MBC3 cart) so its game-select menu works correctly

Fixed a blank-screen hang in Spot caused by the EI; HALT halt-bug being armed while an EI was still pending,
corrupting the interrupt-vector fetch
Fixed the Mr. Do! title screen freezing by latching the STAT LYC-coincidence flag while the LCD is off, instead of
recomputing it from the parked LY

New Auto Layer Transparency option that blends alternate frames to restore flicker-based transparency effects (e.g. ZAS)
Per-layer selector so blending can be enabled independently for background / window / sprites
Per-title "Auto Layer" defaults, with frame-blend automatically bypassed during fast-forward
Fixed blend tearing and SGB flicker, and stopped static GB screens from ghosting; added a blend-mode dropdown
GB blend controls moved into their own "Game Boy Image" group, disabled for SNES titles
GB mix volume now persists in SGB BIOS mode

Hotkey modifiers now mask the GetAsyncKeyState high bit, preventing stray/stuck modifier detection
Input binding fixes: maxKeys is now derived from the Single/Multi combo alone, capture re-enters when the binding
mode changes mid-focus, and the existing binding (rather than ...) is shown on a mid-focus mode switch

Added Libretro support (separate branch) to build RetroArch core.
Copy .info to /info, and .dll to /system
Linux .so is not supplied and user will have to build it on their own from sgb_libretro branch