The jumping enemies thing was a little too hard, until I learned I could fool them by doing a micro-jump, and then it got easy and I felt like I was missing out on some of the challenge. My advice is if you want to add brutally difficult elements to your game, give some kind of long way around it that's inconvenient enough to encourage players not to ignore it, but not so much that player won;t be able to access the game if they can't beat the challenge. My game The Sad Duo is a game about being alone in a two player game and so has puzzles that seem impossible to solve, and that's why I had them be optional instead of block progress with them