Now, many examples of rewards in gamification and otherwise are hybrids of more than one of these categories. Here is one example from World of Warcraft. This is an achievement that you get for various fishing prowess in the game. Yes, if you haven't played W.O.W., fishing is actually a skill in the game. The reward here you get is just a title. So, intangible reward. Just a, something that goes in front of your character name. And there's all these sub components. And some of them are things like, catch a 1,000 fish. That's completion contingent, pretty clear. You catch one fish you don't get it. You catch 100 fish you don't get it. You catch a 1,000 fish you get it. But some of them are different, some of them are performance based and competitive. So, this one here, Master Angler, you only get if you win a weekly fishing contest get the most fish or get certain special reward fish in a defined contest. So, that one actually is not just completion contingent, it's performance contingent, and so on and so forth. There's a mix of different rewards here that are built in and, the point I just want to make here is, there's a lot of complexity that can go into reward design. And in designing gamification, the key is to think about the different possibilities, and come up with the rewards that are most effective in motivating users but as we'll get to in the subsequent unit, also ensuring that there is a truly meaningful and rewarding and valuable experience for those players.