I would like a sudoku app that allows me to easily anotate by selecting a number and then just tapping on each square I want it on, just like this one does. I would also appreciate having a way to either photo a printed sudoku or just building it myself and save several of them for later solving, since carrying magazines just for their one sudoku is uncomfortable.

This isn't critical for me, but if the app also has a tutorial on different solving strategies from rookie to master, it would be great, since it would allow me to keep a single sudoku app on my device.

What app has these features built in?