EmergenceWithPerturbation

globals [changes]

breed [walls wall]
breed [pedestrians pedestrian]

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to setup
  ca
  ask patches [
    ifelse pycor mod 2 = 0 [set pcolor 8] [set pcolor 9]
  ]
  if wall? = true [
    ask patches with [pxcor = max-pxcor / 2 and pycor >= max-pycor / 2 - 1 and pycor <= max-pycor / 2 + 1] [
      sprout-walls 1 [
        set shape "square"
        set size 2
        set color black
      ]
    ]
  ]
  ask n-of n-agents patches with [any? turtles-here = false] [
    sprout-pedestrians 1 [
      set shape "person"
      set size 1.2
      ifelse random 2 = 0 [set heading 90 set color blue] [set heading 270 set color red]
    ]
  ]
  reset-ticks
end 

to go
  set changes 0
  move
  tick
  if ticks > 5000 [stop]
end 

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to move
  ask pedestrians [
    ifelse any? other turtles-on patch-ahead 1
      [
        ifelse random 2 = 0
          [if ycor < max-pycor [if not any? pedestrians-on patch xcor (ycor + 1) [set ycor ycor + 1 set changes changes + 1]]]
          [if ycor > min-pycor [if not any? pedestrians-on patch xcor (ycor - 1) [set ycor ycor - 1 set changes changes + 1]]]
      ]
      [
        fd 1
      ]
  ]
end