Vector.Animation.CircularMotion = function(_self,_center,_speed)
  --[[
  CircularMotion takes a position a center and a speed,
  given the position and center, find a vector dif from center to start_vec,
  use the magnitude of dif to find the circle radius, use the angle between the components of dif to find the start location on the circle,
  set the step to the appropriate starting location
  ]]--
  local dif = _center - _self
  local radius,step = Vector.magnitude(dif), atan2(dif.x,dif.y)*framerate/_speed

  local function update(_end)
    while not _end do
      step += 1
      _self:Set(-cos((step/framerate)*_speed)*radius + _center.x,-sin((step/framerate)*_speed)*radius + _center.y)
      yield()
    end
  end

  return cocreate(update)
end