Package this with some of your other games to create a 'Compendium of Games'. Each game tends to be too short. Including several different games would make it a game worth buying.

You could have two or three i.e. Compendium of Games 1, Compendium of Games 2 etc. (or a better title would be 'The First Compendium of Physics based Games', 'The Second Compendium..........' etc. Each compendium having a different theme for example physics based puzzles as one compendium and those throwing games as another compendium.