In this chapter, we'll define a rule set for our game, which will guide the player through the gameplay experience. We want to give the player the ability to start the game and immediately identify what they have to do in order to win the game. In its most basic form, a game could be defined by the win condition and the steps the player can take to reach that win condition. Ideally, we want to ensure that each step the player takes toward that goal is fun.

We'll begin by applying some constraints to the player in order to increase the level of difficulty. A game without a challenge quickly becomes boring, and we want to ensure that every mechanic in our game provides the player with an interesting choice or challenge. We'll then set up a goal for the player to achieve, along with the necessary adjustments to our enemy targets to make that goal challenging to reach.

In this process, we'll work to accomplish the following:

• Reducing stamina while the player is sprinting as well as regenerating it while the player is not sprinting
• Preventing the player's gun from firing if they run out of ammo
• Creating ammo pickups that allow the player to regain ammo
• Defining a win condition based on the number of targets eliminated
• Creating a menu that allows the player to replay or quit the game upon winning