GB games with anamorphic widescreen support for GBA display
Made this prototype to see if the "full screen stretched" mode on the GBA when playing a GB game could actually be useful. The game simulates an 8x12 tile mode, which when stretched on GBA 50% wider looks correct, and you have a proper widescreen GB game using the full resolution of the GB.
I wonder if anyone else finds this concept interesting. Maybe something like a horizontal space shooter could really benefit from a widescreen aspect ratio on GBA, while also supporting the old school Game Boys in a letterbox mode using regular 8x8 tiles. So far I think no games have ever done this.
In order to do this you need each 8x12 tile to be represented by one 8x8 tile consisting of the top two thirds, one consisting of the bottom two thirds, and one of the bottom third plus the top third of every other possible neighboring tile.
The 256 unique background tile limit on Game Boy will allow 15 unique 12x8 background tiles using this method (21 for GBC), which can obviously be increased through smarter memory management. The code that assigns them during gameplay is light on the CPU. It allows for a visible area of 20x12 virtual bkg tiles. Color palettes could be adjusted using LCD interrupts every 12 scanlines. Adding sprites is easy, since they can already be set to 8x16 mode.