* If you are using overscan, consider that the position of the screen may not be the same on all monitors, so a method to centralise it before the game starts, or in the options of the game.
* It should be possible to redefine the keys to the choice the user wants, or to be able to choose from a preset list. Good key "presets" are cursors and space xor copy (good for cpc6128 CPC6128 and Plus more awkward for 464 and 664), q for up, a for down, o for left, p for right and space for fire.
* Games should support the FIRE 2 button for gamepads/joysticks. Maybe the player character needs to be able to jump, and then UP is used for this. And that is ok. Just don't forget to include the FIRE 2 button for jumping as well.
* Consider supporting AMX Mouse (or compatibles such as Bryce's USB mouse hardware) and Symbiface 2 Mouse where it makes sense in the game. Movement could also be used for moving to the wanted menu item and clicking the mouse button to select.