A rigid polygon with a unique name and the following parameters:

- position: The X/Y position of the center of mass of the polygon, relative to the center of the world.
- angle: By how much the polygon is rotated in positive direction, that is clock-wise.
- velocity: The velocity of the center of mass of the polygon. Unit: meters/second.
- angular velocity: How fast the polygon is spinning in positive direction, that is clock-wise.
- mass: Total mass of the polygon. This influences forces with which the polygon interacts with other items.
- inertia: How difficult it is to change the polygon's rotation.
- momentum: A fundamental quantity in mechanics that is conserved in the absence of external forces. A product of the mass and the velocity.
- angular momentum: Measure of the extent to which the polygon will continue to rotate unless acted upon by an external torque.
- kinetic energy: The work needed to accelerate the body of a given mass from rest to its current velocity.
- vertexes: A list of vertexes (corners) of the polygon, which define its size and shape. Coordinates of each vertex are relative to the center of mass of the polygon.