TRAILS SOURCE CODE
Turtle Procedures Observer Procedures

to setup
seth 0
if (who = 0)
    [setc red
    setxy x1 y1]
if (who = 1)
    [setc blue
    setxy x2 y2]
end

to go
fd 1
ifelse pc = black
    [stamp color
    rt 90]
    [stamp black
    lt 90]
end

to setup
ca
crt 2
ask-turtles [setup]
end