The number one mistake that people make is thinking of gamification and product design as two completely separate processes. If you spend a lot of time and effort designing a product to do a specific thing, and build a good user experience around that thing, adding gamification at the end will only disrupt that user experience.
Instead, think about fun from the very first design meeting. Make sure each interaction on your app is pleasurable and coherent. This requires thinking ahead, but it's more than worth it.
The simplest expression of gamification, and the one people usually think of first, is also the least useful. Of course I'm referring to badges, points, and leaderboards.
But if the rewards are not meaningful, they can't motivate anyone. Imagine someone has asked you to do something you don't want to do. For instance, alphabetizing a bookshelf in somebody else's house. You're not motivated to do this because it is tedious and will not benefit you.
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