Battery usage / cant fill in notes

This app runs down the battery on my iPhone 7 plus with very little apparently going on. Its Sudoku; the app should only be waiting for my input. Also, I like to fill in the notes with all numbers that do not exist in the box, and then take away what I see in the rows. That way I can focus on one region of the puzzle at a time. This app does not let me fill in a hint if the number exists in a row. Would rather have the option to make an error so I can play the way I want.

staticv0id about ⋆Sudoku, v2.3.11