High Difficulty from the Start

I failed multiple times even on low-level challenges due to high difficulty. I think it's designed with the assumption that players will use CMs (commercials/ads) or in-app purchases to progress. Some hard difficulty challenges required watching CMs to unlock. The high difficulty makes it a good way to kill time, and it's fun when you finally solve them. The retry CMs aren't too long, so it's quite enjoyable.