Experience bars -- These measure our incremental progress and help us visualize how far we've come and how far we have to go.
Multiple long- and short-term goals -- These are our main quests and side quests, which are broken down into smaller tasks.
Rewards for effort -- Every bit of effort exerted in a game is rewarded through credit, such as gold, loot and experience.
Rapid, frequent and clear feedback -- This clearly links actions to consequences, which makes learning easier and faster.
The element of uncertainty -- This is the neurological gold mine: we keep going because we want to find out what's next.
Windows of enhanced attention -- Gameplay helps boost memory and confidence. Game players are more willing to take risks and pursue difficult tasks.
Other people -- Gameplay gives us a chance to connect with multiple players online.