Really fun game! The puzzles in castle 2 are a lot better than castle 1 - with that said, I feel like there were a few puzzles where the solution was easy to find, but I failed the timing to jump onto the spring multiple attempts in a row, and in puzzle design you don't want the time between discovering the solution & successfully accomplishing it to be too long (especially since this game bills itself as being playable with the on-screen buttons in theory). Maybe if there was a little pause when pressing left/right so you don't have to react to your own movement/turnaround immediately?
When you replace the Kenney spaceman, maybe the original character should be some sort of charging knight/cavalier, which would explain why they constantly travel in the same direction when you press an arrow key.