We've seen puzzles like this in the past.
1. The higher levels have rectangular shapes, which obviously makes it harder.
2. I did the first dozen levels pretty quickly, but I've tackled this genre before so I knew how to approach it.
3. I skipped to 100 and really liked the strange shapes. But still solved it fairly quickly.
4. Then I jumped to 150: very tough!
5. Love the graphics.