This the real split-screen approach, so Donkey and Diddy have independent controls and their own cameras, with one view above the other. Both views share the same world and game simulation, so Player 2 can explore without constantly being pulled back to Player 1. At this point, I’d say almost the entire game is playable and completable in co-op, although there are still scenes and combinations I haven’t fully checked. I recommend saving at the start of each level while the remaining edge cases get ironed out.
Some info:
The object pool has also been expanded from 25 to 89 actors, giving the game room to keep objects active around both players. A lot of work went into fixing problems with banana pickups, deaths and DK-barrel rescue, ropes, animal mounts, minecarts, barrel cannons, camera transitions, palettes and HUD rendering. Testing covered caves, underwater levels, minecarts, bosses and ropes in both native and widescreen modes. Repeated runs produced identical results, and saving/loading midway through a run matched uninterrupted play.
There’s a Windows release available here, and I’ve submitted an upstream PR. Enable Mods > Simultaneous co-op and configure Player 2 in Controls.
Really happy to share this!
p.s. Big thanks to elliotttate for original recomp