and play, but periodically or persistently, the game will show an advertisement to the user which they will have to watch through before they can continue with the game. The developer earns revenue from the advertising network. In some cases, an in-app purchase allows the player to fully disable ads in these games. Subscription model A subscription-based game will offer a base version with limited features that can be played for free, but additional premium features can be obtained if the user pays a monthly subscription fee. If they terminate their subscription, they lose access to those features, though typically not any game progression related to those features, and can pick up those features later by restarting their subscription. Many game apps are free to play through a combination of these models. Over time, mobile developers of these types of apps have observed that the bulk of their players do not spend any funds on their game, but instead revenues are generated from a small fraction, typically under 10% of their total players. Further, most of the revenue is generated by a very small fraction, about 2%, of the total players, who routinely spend large amounts of money on the game. A similar split on revenue had been seen in social-network games played in browsers. These players are known as "whales", inspired by same term used for high rolling gamblers. The social nature of a mobile game has also been found to affect its revenue, as games that encourage players to work in teams or clans will lead to increased spending from engaged players. Common limits of mobile games Mobile games tend to be small in scope (in relation to mainstream PC and console games) and many prioritize innovative design and ease of play over visual spectacle. Storage and memory limitations (sometimes dictated at the platform level) place constraints on file size that presently rule out the direct migration of many modern PC and console games to mobile. One major problem for developers and publishers of mobile games is describing a game in such detail that it gives the customer enough information to make a purchasing decision. Location-based mobile games Games played on a mobile device using localization technology like GPS are called location-based games or location-based mobile games. These are not only played on mobile hardware but also integrate the player's position into the game concept. In other words,