Made it through two bosses.
Died to a spring next to a pit.
The jumping Kappa in the first sections of the game seemed to be the biggest contributor to lag spikes in the game. I think the descending spiked platforms also did to a lesser degree, too.
But overall, the game played well, looked fantastic, sounded great. If someone told me it was some long lost GameBoy game, I think I'd be inclined to believe them. Well done.