Target Quake Arena is a mod that changes Q3A/OA gameplay to 2D. It uses its own, expressly-designed maps. You will see your character from a lateral view, and you will be able to move left and right, to jump and to crouch, but not to directly move in depth. There are however multiple depth planes that can be reached by using teleports; you can hit only the players in your same depth plane. Maps scroll both horizontally and vertically as you move around the arena, and you can push the zoom button to see at longer distance ahead your character. You turn yourself left or right and accurately aim by moving around your mouse (a crosshair will help you), so you can run in a direction and shoot in another one, like in the regular Q3/OA.