Limited time offers with unnecessary urgency.
"Every event is timed with limited rewards and many shop transactions have temporary discounts"
"They often have events that have their own currency and half of the items you get (unlocked via getting a certain amount of the limited time currency that if rewarded by doing everyday tasks) you only ACTUALLY get when you get enough of a different not event linked currency"
"Heroes only available for a limited time. Or special offers that don’t show up very often"
"Seasonal decorations in exchange for points you gain for completing orders - they sell discounted bundles for energy and diamonds so you can keep playing and collect these decorations"
"The game might offer energy bundles at a discount for 10-15 minutes after you've run out."
"There are many seasonal events that you have to play constantly to finish."
"the game is always running special events that add cosmetics and new levels to the game. the cosmetics can only be purchased while the event is active and the levels cannot be purchased, only playable while the event is active. sometimes they offer brief limited time offers on their valuable boosts"