Find out why he wants the NDA. Sometimes it is because they don't want it publicly known that they hired a freelancer to do the work. He might not want you shouting from the rooftops, "hey, I was the one who built this!"

If that's the case you can word the NDA so that it gives them what they want and you don't give up anything you don't want to give up.

It could also be that in order to implement the game (or whatever) you could require access to business strategy information (like pricing, upgrade dates...) that they want to keep secret. You can word the NDA to cover this but not the technical stuff.

Or if none of this applies then you can point out that NDAs don't cover information that is available publicly so any "ideas" typically won't be covered once they are publicly available.

And as others have pointed out always have your own template to start from.