When writing your description it is useful to think of the game as a robot which manipulates a collection of objects. Each time an event occurs (user input, timer event etc) the robot changes the state of objects and updates the image on the screen. Each object has properties defined by a set of fixed parameters, a changing state (e.g. position and velocity) and knobs and buttons for changing this state (actions). The game description should contain the following elements: • The overall description of the game. This description has to be sufficiently detailed: all objects must be introduced and described, and their behavior defined. • The list of objects; for each object it is usually convenient to specify fixed parameters needed to create an object of this type, the state, that is, the list of object parameters that may change (e.g. position) and actions that can be performed on (or by) the object. • A description of game controls and how these controls change the state. These descriptions are intended as a foundation for designing C++ classes implementing various objects. Game description. Two players play the game. Each player controls the vertical motion of a paddle (represented by a rectangle) on the screen using two keys on the keyboard. A ball starts in the center of the screen and initially moves in a random direction. When the ball reaches a wall or a paddle, it bounces. If the left wall is reached, the right player scores a point; if the right wall is reached, the left player scores a point. Objects. Ball. Fixed parameters: initial velocity, initial position, radius, color. State: position, velocity. Actions: draw, check for intersection with a line segment or rectangle, change velocity for a bounce