First of all, the classical way is to sell your application at a fixed price. The customer pays once and then plays the game as long and as many times he/she wants.

The problem for you as a developer, in this case, is that you will lose a lot of sales due to piracy of the game. This problem even exists in the app stores and markets these days.

This is another method that is used for commercial games and for free games too. People pay a monthly/yearly subscription fee to be able to play the game or to get access to better features in the game. The subscription model was successfully introduced by World of Warcraft and other such games.

One method is to give out your app/game for free. To make money, you can display advertisements inside the app. This can be a rotating banner ad located at the edge of the canvas or a full-screen ad interrupting the game at one point. Displaying a full-screen ad will block the player from proceeding further for a while and is often seen as an interruption to their game play. As you can imagine, most players have a negative opinion about this.

No matter what kind of ads you use, one way to earn money from this is when people actually click/tap on these ads. Another way is by just displaying ads for as much time as possible. With the latter method, it isn't necessary for the customer to interact with the ad, but it needs more ad impressions to be displayed to bring in some serious money. In this chapter, we will implement ads that generate money in both ways.

Releasing an app for free with ads also almost erases the piracy problem, as everyone can download the app for free. However, be aware that on open platforms such as Android, people are already using Ad-blockers. Also, your app needs to have online access to display advertisements.

The last common method here is In-App purchases. These are extra features of a game that are available once the user purchases the In-App item. There could be extra levels, more weapons, removal of advertisements, and so on. You can implement this in a free app or in a commercial one; it is your choice.