The best collection I know is https://www.chiark.greenend.org.uk/~sgtatham/puzzles/ https://www.chiark.greenend.org.uk/~sgtatham/puzzles/ which has ports for va

The best collection I know is https://www.chiark.greenend.org.uk/~sgtatham/puzzles/ https://www.chiark.greenend.org.uk/~sgtatham/puzzles/ which has ports for various platforms (in my case using android, but apparently there's an iOS port too, see links at the end). The games have various difficulty levels to choose from.