# Main Command: Go
# Tree (Random Branch Length) 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
  If :Length< 10 [Stop]     # ends recursion if branch 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 * Pick [0.7 0.75 0.8] Right :Angle
  Tree :Length * Pick [0.7 0.75 0.8] 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
  Repeat 12 [  
    New PenUp Back 160 PenDown
    Make "Angle 60 Tree 80 Wait 200]
end