For two-player games (and some one-player games as well) it is always important to have a keyboard input method that allows two or more buttons to be pressed simultaneously.
On the ZX81 and the other Sinclair computers this can be achieved by using the in_KeyPressed() function, which returns the current state of a specific key.
dom wrote:We'd need to write alternate keyboard handlers for all the ports and there's not usually masses of information available on the ports and scancodes.
Stefano has added two pseudo joysticks (on the number keys) so multiplayer would be supported at the moment, but no one has had time to create a complete keyboard scanning routine.