# Main Command: Go
# Tree Animation by Guy Walker
# www.logoarts.co.uk

to new
  # set default screen, pen and turtle
  ResetAll SetScreenSize [400 400] HideTurtle
  SetSC Black SetPC Green SetPS 1 PenUp
end

to tree :length :angle
  If :Length < 10 [Stop]     # ends recursion if length too small
  SetPW :Length/9     # reduce pen width as branch length gets smaller
  SetPC TreeCol :Length     # branch color depends on length
  Forward :Length Left :Angle/2
  Tree :Length*0.71 :Angle Right :Angle     # tree with 0.71 branch length
  Tree :Length*0.71 :Angle Left :Angle/2
  PenUp Back :Length PenDown     # return to starting point
end

to treecol :length
  Make "Green Round 2.5*(100-:Length)     # green depends on length
  Output ( List 255 :Green 0 )     # red set to 255 and blue to 0
end

to go
  New Animation Back 150 PenDown
  For [Angle 0 180 4] [     # angle from 0 to 180
    Wash Tree 100 :Angle Refresh Wait 20]
end