Zero ads or alike spam. Clean interface, enjoying a game that allows me to focus. Level packs for approx. 1.75euro for 30 medium or hard levels are a good business model IMHO. I got my 6YO hooked on this thanks to eliminating possibilities in pencilmarks mode, which is a quite satisfying way of solving I haven't previously ran into. I wish there were buttons allowing crossing all occurrences of a number in a given row, column or square. Shop should allow buying several packs in one payment.

Lovely app, horrible graphics. When a box is highlighted, the 'bold' lines do not allow to see how many cells in the sum. Conceptis have other SUDOKU puzzles whose graphics are great.