A new 20 question drag and drop quiz game has been added to the micro section of the site. This one covers rival vs non-rival and excludable vs non-excludable goods. Check it out and let me know what you think in the contact link at the bottom of the page.
Here is a run-down of public goods, the free rider problem as well as what rival vs non-rival goods and what excludable vs non-excludable goods are. I hope to have a game to practice sorting these different types of goods soon.