0 done or available from within an app (= piece of software for your phone or computer that has a particular purpose): --
Twelve additional levels can be downloaded after an in-app purchase.
Although a free app, customers are able to buy in-app purchases.
Some users who had made in-app purchases discovered that their purchases had disappeared.
The application includes several free music scores, and additional music scores can be acquired through in-app purchasing.
They have also produced branded apps for several publishers using the freemium model with in-app purchasing.
The game follows the freemium model of game monetization with in-app purchases as the largest source of game revenue.
Each enemy destroyed provides the player with more in-app coins to obtain new towers and upgrade existing towers for more damage output.
Equipment can be purchased with either the goldball currency earned through gameplay or via in-app purchases.