Chess Challenge!
Chess Challenge! is an app with lots and lots of checkmate challenges.
Every puzzle has a way to force checkmate in a certain number of moves. Once you solve the puzzle you get a new one! Never ending chess fun!
You can also reset a board, undo, and get a hint. Some boards have multiple solutions but a solution is guaranteed to be there! These challenges are based on real games and new ones are being submitted all the time.