anchor: love.physics.newFixture
  Creates and attaches a Fixture to a body.
  
  Note that the Shape object is copied rather than kept as a reference when the Fixture is created. To get the Shape object that the Fixture owns, use Fixture:getShape.
  fixture = love.physics.newFixture( body, shape, density )
  body Body The body which gets the fixture attached.
  shape Shape The shape to be copied to the fixture.
  density (1) number The density of the fixture.
  fixture Fixture The new fixture.