I think the game is worth 5 bucks. The only thing that makes it a "challenge" are the achievements. This is that rare time when achievements actually add something to this game.
With that being said, after wasting 5 hours of my life on the last 2 levels and constantly fucking up at the very end to ruin the 5 in one go (time, star, no death, all balloons and whatever the 5th criteria is for beating levels). I realized you can just go into the bonus stage and grab the hit deflection and pummel through problem levels. I feel cheap doing that but after 500 retries I deserved it.