I guess we can all agree that Numpad is the last place to see a person gaming so why not. The basic idea is to make a proper game based on the theme that may cover additional missions using such controls and making them in such a manner that they are Adaptable. If you don't have a Numpad or don't like the idea of trying to make a game on Numpad controls then it is fine to add other controls along with the numpad controls. you can also use touch controls and mouse and gamepad controls but make sure that the numpad controls work as well. 

 STARTING IN 3 DAYS and it lacks participation. The themes and additional missions will be out soon. Numpad Jam #1 - itch.io