Nice, Challenging Problem Set!

I like this tsumego app. It offers a nice little handful of problems for free, and the problems range in difficulty from what feels like 12 kyu to ?? dan. I only wish 1) it offered more problems for free as many websites already do and 2) it were a bit more forward about its problems difficulties since I know the app has been demotivating to my beginner friends.

Shoja about Tsumego Pro (Go problems)