Although some of the game's first-person mechanics were first prototyped in the "Battlefield 2" engine, "Mirror's Edge" was built using Epic Games' Unreal Engine 3 because DICE's own Frostbite engine was still in the early stages of its development cycle when production of the game started. Creating all the first-person animations proved to be an ambitious task, but it was considered essential to help orient players in the game world. The game has hundreds of first-person animations and simple moves like using a ladder has over 40 animations alone. These include interactions such as jumping into it from multiple positions, climbing it up or down, or hanging on it with one hand. Although the game has a believable first-person perspective, it is not meant to be a simulation. For example, the player is able to stop quickly after a full sprint because the development team felt that keeping the inertia would make the gameplay irritating. To animate the character's in-game shadows, a different animation system runs simultaneously. The only information that is visible in the game's heads-up display is a small reticle in the center of the screen, which was added to lessen the simulation sickness associated with the free movement of the camera in first-person view.