This is a UI/UX revamp of a GPL-licensed puzzle game. It's a KenKen game, forked from MathDoku 1.9. For those who don't know what KenKen is, it's like Sudoku but much more interesting with added mental maths. The goal is to fill in the entire grid with numbers while meeting the operation restrictions for each grid cage. Eg. '9+' means all the numbers in a cage have to add up to nine.
Highlights include unlimited puzzles with different mathematical modes, undo functionality, statistics tracking and puzzle screenshots.
Get it from Google Play.