LookAtMyGame have published a dozen Casual Games on both iPhone and Android. The Goal was “Games with instant Fun but Hard to Master”. So everybody can play those games, from child or grand parents but these games are still interesting for experienced players because levels are slowly increasing in difficulty and so it represents challenge to finish game at 100%.
All of those games are Freeware, it means that it is free on AppStore and Google Play but it contains advertising. You can rid of those advertise via an inApp purchase.