After completing a few lessons, you'll unlock leaderboards. These match you up against similarly skilled players, where the 'promotion zone' always feels within reach.
What'll make this so effective is that the promotion zone isn't too challenging—it just requires a few more minutes of activity.
In fact, Duolingo might populate the lower half of the leaderboard with bots. It doesn't matter, it all creates a sense of social achievement by completing more lessons.
And by introducing it after you've made some progress, they're leveraging the Goal Gradient Effect.
Hopper is a price tracking app for flights and hotels, and it frames the value of a booking by showing a timeline of the predicted prices over time.
When rating a book 5 stars, you'll see a celebration burst onto screen.
If you attempt to use a blocked app, OneSec offers a variety of novel interventions, like opening the front camera so you have to stare at yourself breaking your own rules.
After ordering a food delivery, you can easily create an event in your calendar with all of your slot information and booking reference.
Octopus Energy will let you earn Octopoints for completing habit-forming actions (like submitting meter readings), which you can then redeem for credit.
Loom will let you easily swap the default selection of emojis for your most frequently used ones.