That is one limitation that I'm going to try and stick with, but I don't know if its a rule. I really need two action buttons for my idea but have come up with a way to possibly do it with one to match the Atari 2600 joystick.
I guess you probably wouldn't get judged if you added an extra button, but maybe not a whole keyboard of keys. My answer is just an opinion. So don't take it as an official answer.
yes you have to stick with how many buttons are on the controller, for example the NES has 6 buttons so your game would have a limit of 6 buttons, game boy same thing and atari has 5 button so 5 controls. hopefully that makes sense :)
