Nice but room for improvement
ActSudoku has fairly slick UI and feature rich. It needs are few tweaks and bug fixed to reach 5-star status: (1) lighter color for unmarked quare/numeric (current gray is way too busy and distracting), (2) suspended games are frequently lost, (3) commit on a tiny UI is error prone (should pop out like the QWERTY keyboard, and (4) no wooden wallpaper.
Nutmac about
Sudoku Uno: Unlimited Sudoku