In the CPC world it is more common that a game supports both keyboard and digital joystick for those users who don't own joysticks.
In addition, it is also nice if the keys could be redefined but that is not necessary.
The standard CPC can handle 3 joystick buttons, but many CPC joysticks have only 1 button.
The CPC+ and GX4000 can handle 2 joystick buttons only, but the Amstrad joypads provided with the machine have 2 different buttons.
There are some common keyboard configurations used: