Once I reach the Great Castle level, performance completely tanks on my mac and the game becomes unplayably laggy. Sometimes it's immediate on loading the level, other times it kicks in once the beams come on screen. If I press ESC, the menus are lag-free.

Not sure how to get past the rock where you meet john. It says press x and left but nothing I press is working. Did I miss something, or can I just not read what it ACTUALLY says?
Other than that issue, it's a cute game. I just wish I could get further in it...

Edit: the "B" key should be made a lot clearer in-game. A lot of other controls also are not explained in-game. Yes, having them in the description helps, but a game shouldn't have to rely on the description to explain the controls to the player.

For some reason in the third stage, you can just walk to the left of the giant slime and fall off into oblivion.

Very nice and challenging platforming. My only problem was the wall-jumping, unless I was doing it wrong, it's really wonky and hard to do well. The music great and fits along the level quite well.

Very fun game! The graphics are amazing (particularly love the backdrops and slime sprites) and the music works well doing a good job of adding atmosphere to the game, however, as many other reviews mention the controls can be difficult to handle, particularly with long wall jumping segments where by the time I was actually able to complete the wall jumping segment my hand would be tired. I also assume this was a glitch but during the slime boss fight, I was able to run through all the enemies and bullets without taking damage. The controls and game do run fluidly though, despite some issues with difficulty curve in the wall jumps, as well as the fact that when wall jumping the wall pushes you away from it which creates difficulty when trying to jump up from the wall, and Hans' ability. I did however really love the moving platform segments in the village level, and the boss fight as it required some amount of rythm and the coin challenges providing extra reward.
Overall really good game that could use some control tweaking but definitely something i'd recommend playing!