Please be aware updates have stopped again. The app is appropriately named in that it offers a broad range of problems suitable for beginners. It does not provide much in the way of written feedback, instead allowing players to work through solutions where they can. Besides the daily puzzle, it has a very large database of problems to choose from. Customer service is outstanding. I have several times reported issues and they have been fixed within a day.
Some correct solutions are become failure solutions
not working
Concentrating to a problem is almost impossible with an ad flashing right next to it.
Lots of high quality tsumegos.
This program is harder to find in Google play. Good for reading skills. Excellent tool for absorbing stress when ready to snap from big city bs.