La densidad del collider utilizado para calcular su masa (cuando la masa automática está habilitada).
When using Rigidbody2D.useAutoMass, increasing the collider density increases its
mass - as does increasing its area - as the collider mass is calculated as a product of density and area.
Note that by default, Rigidbody2D.useAutoMass is disabled, so the mass of the collider is set directly by Rigidbody2D.mass, and this density value is ignored.
See Also: Rigidbody2D.mass, Rigidbody2D.useAutoMass.