 # constants
-qt  = Math.PI / 2
-tau = Math.PI * 2
+pi  = Math.PI
+qt  = pi / 2
+tau = pi * 2
 
 # general handle on everything; keeps track of geometry of entities it contains
 class Universe

    [ x, y ] = @edgePoint a
    @drawCircle x, y, @eyeSize, 'black'
  drawTail: ->
    a = @angle + Math.PI
    [ x1, y1 ] = @edgePoint a
    [ x2, y2 ] = @edgePoint a, @radius + @tailSize
    c = @ctx()

  margins: ->
    m = @marges ?= []
    return m if m.length
    fi = pi * @visualAngle() / 2
    t1 = @angle - fi
    t1 = @universe.tp( Math.sin(t1), Math.cos(t1) )
    t2 = @angle + fi
