Making a working Sega Genesis rom for this is insane, I love it! The visuals and audio aspects were great and felt very Genesis-ey as well!
There were a few things I wasn't big on, though, mainly the level design felt kind of unfair at certain points (which I guess kinda adds to the Genesis feel), and the first boss had a bit too much health in my opinion. Neither of those were bad enough to ruin the game for me, though, especially because the game was very generous with its checkpoints (and oh my god thank everything you didn't include a lives system).
Overall I think its very cool and pretty fun! Also the final boss was a really fun challenge but still felt fair!