to alongseg
fd 20
lt 60
fd 10
rt 120
fd 10
lt 60
fd 10
end

to biggertile
repeat 4 [pu lseg rseg bigtile lt 90]
end

to biggestile
repeat 4 [pu lseg rseg lseg rseg biggertile rt 90]
end

to bigtile
repeat 4 [pu lseg rseg pd tile rt 90]
end

to grid
repeat 3 [upseg pu rt 180 upseg rt 180 pd rt 90 alongseg lt 90]
upseg
pu lt 90 repeat 3 [alongseg] rt 90 pd
end

to gridline
repeat 3 [grid]
rt 90
repeat 3 [alongseg]
end

to lseg
fd 0
rt 60
fd 10
lt 30
fd 5
lt 30
end

to rseg
fd 0
lt 60
fd 10
rt 30
fd 5
rt 30
end

to tile
repeat 4 [lseg pu rt 180 lseg pd rt 90]
repeat 4 [rseg pu rt 180 rseg pd rt 90]
end

to upseg
fd 10
rt 90
fd 10
lt 90
fd 10
lt 90
fd 10
rt 90
fd 10
end