We have our first AppyNation guest post from Games Industry Consultant Jamie Firth! You can follow Jamie on Twitter here: @mrjfirth

I’ve bored many developers with this in the past: a little thing I like them to think about when considering any design mechanic for a video game. It’s pretty much universal across all genres, and although the rule won’t help you design per se, if you bear it in mind whilst you are designing then I can pretty much guarantee less frustrating moments for the user.

You CAN also test to see if you have broken the rule very easily and adapt if so.

Broken down, there are only two inputs that a player has in any game situation:

Decision: What do I want to do?

Action: How well did I do it?

Whatever DECISION the player makes or how well they ACTION it, Firth’s Law says:

DECISION + ACTION must equal a fair and understandable outcome.

If the outcome is success, the player should be rewarded and it should be clear they were correct on both counts.

If the outcome is failure, the player should be punished, but it should be crystal clear as to whether it was their DECISION or their ACTION that was to blame.

For example: In a platform/adventure game there is a gap to jump. The player must decide what to do (“I’ll jump it”) and then carry out the action.

The user first attempts the jump and falls to their death. Here, it should be clear which part of their input was wrong:

“I jumped a few feet before the edge of the platform, and I missed the other side by about the same few feet – My jump was bad”.

“Well, I jumped right from the edge of the platform and missed the other side by quite a way – Maybe that’s not the way I am supposed to go?”

In the case of “b” above, there may be a different reason (commonly in this situation it would be because there is another way to jump further (sprint-jump, double-jump, gravity boots etc) at which point there should be a hint “How can I jump further?” and after a few unsuccessful tries a more blatent hint: “Maybe if I sprinted/double-jumped/etc.”.

This all seems very basic stuff, but you’d be surprised just how many times, when you think about it, designers seem to have lost sight of this most simple of rules.