Dev here! Thanks for your feedback, it means a lot!
I wholeheartedly agree that the jumping can be a little precise, especially for the first few levels. I constrained myself to 16x16 tiles, which means the player's jump height can't be too high if I want to make long levels, which means I can't allow a large timing window to jumps. Most jumps are a little precise because of this.
I think the levels themselves can also be a little difficult. I was only able to get three play testers on board, and two of them played the easier levels after they'd already had some experience with the game. I tried to make the first and second levels as forgiving as possible, but I wasn't really able to get a good gauge on how easy the first few levels were for new players.
I'll find a couple new players and ask them whether they thought the first few levels were too hard, and make changes accordingly. I'll also use what I learned for my next games!
Edit: Also, if you're having trouble and a jump just seems impossible, consider looking for another way to beat it! Don't be ashamed to look at the walkthrough if you get stuck.