Like how you have to complete a field. That is addicting.
The difficulty curve makes it very difficult for me. That's why I quit at lvl 4. I liked the new mechanics you used. One thing you could do is make some levels with 1 mechanic, this can be 2, 3 , I like 5. And then make each level with the mechanic more difficult such that it has this difficulty curve: https://featherhatgames.com/105-2/ (red is a new mechanic)