Ask HN: How to teach a 12 year old to make JavaScript games?

I am teaching my 12 year old cousin how to program Javascript (currently with Codecademy).

He is doing pretty well and finished the Javascript course. Now he is very interested in learning how to build Javascript games.

I have no experience with games, it seems pretty hard to me cos (I think) you need to know both programming and graphics.

I am looking at the source code of 2048, I think it might be too advanced for him.

Question: What is a good way to teach a 12 year old to make Javascript games?