Which lever to pull: more chances or a better rate
Payout is chances times value per chance times the rate. Users feel the count and barely notice the rate, so the count is the lever that changes behaviour.
Tagged “retention”
3 entries
A daily task list that resets cleanly
Generate the day's tasks once, track progress against a date key, and pay the completion bonus exactly once — no midnight cron required.
Achievements that reward the behaviour you want
A table of conditions, a checker that runs after activity, and a unique key so an achievement can only be awarded once.