\VDDdef M(0,0)L(-4,-4)R(4,4) % L and R stretch the viewport to keep the circle visible
\VDDdcanvas 1:1
  \VDDdcircle M:4 
  \VDDdpoint M % draw single point
  \VDDdline P(4;52)Q(4;170) % draw line with endpoints on circle
  \VDDcavg S:PQ 
  \VDDcabstransp C:S:SQ:2   % go 2 spaces from S in direction of SQ, call result C
  \VDDcavg N:CM
  \VDDcplength\length:NC    % calculate radius of small circle
  \VDDdcircle N:\length{}   % draw circle
  \VDDlcirclepointletter PQ:M:1
  \VDDlcirclepointletter M:N:1
  \VDDdeflinepoint l:PQ
  \VDDlcirclelinepointletter l:NS:1:1
  \VDDlcirclelinepointletter l:NC:1:1
\VDDdcanvasend
