Substitution Best-Shot Public Goods Game

; a model for the 'best-shot' public goods game

globals [
  selected
  turtle1
  turtle2]

turtles-own [
  action        ; action (either 0 or 1)
  orig-action   ; each person's initially assigned action
  action-1-sum
]

to setup
  clear-all
  set-default-shape turtles "circle"
  ask patches [ set pcolor cyan + 1 ]
  set selected nobody
  make-turtles
  distribute-actions
  create-network
  select-nodes
  delete-nodes
  add-nodes
  reset-ticks
end 

; create the turtles in 1-dimensional lattice

to make-turtles
  create-turtles num-nodes [
    set color black
    set action 0 ]
  repeat 50 [layout]
  ask turtles [ setxy 0.95 * xcor 0.95 * ycor ]
end 

to layout
  layout-spring turtles links 0.5 2 1
end 


; initialize some individuals to start with action 1

to distribute-actions
  ask turtles [ set action 0 ]
  ask turtles [
    set orig-action action
    update-color
  ]
end 

to update-color
  set color ifelse-value action = 0 [black] [white]
end 


;; create the links in the network

to create-network
  ask turtles [
    let nbrs other turtles in-radius 10
    ; other omits the turtle itself
    create-links-with nbrs [ set color white ]
    ; only one undirected link between any two turtles is created
  ]
end 

to reset-nodes
  clear-all-plots
  ask turtles [
    set action orig-action
    update-color
  ]
  reset-ticks
end 

to redistribute-actions
  clear-all-plots
  distribute-actions
  reset-ticks
end 

to go
  ask turtles [check-neighbors]
  ask turtles [ take-action ]
  ask turtles [ update-color ]
  tick
  ;debg-actions
end 

to debg-actions
   ; debugging, show actions of all nodes
  foreach sort-by[ [a b] -> [xcor] of a < [xcor] of b ] turtles [ i ->
    ask i [ show action ]
  ]
end 

to check-neighbors
  set action-1-sum sum [action] of link-neighbors
end 

to take-action
  let num-neighbors count link-neighbors
  set action ifelse-value (action-1-sum >= 1) [0] [1]
end 

to select-nodes ; use the mouse to select which nodes take action 1
  set selected min-one-of turtles [distancexy mouse-xcor mouse-ycor]
  if mouse-down? [
    ask turtles with [distancexy mouse-xcor mouse-ycor < 2] [
      set action 1
      update-color
      display ; update the display
    ]
  ]
  set selected nobody
end 

to add-nodes
  if mouse-down? [
      create-turtles 1 [
        set color black
        set action 0
        setxy mouse-xcor mouse-ycor
        let nbrs other turtles in-radius 10
        create-links-with nbrs [set color white]
    ]
    stop
    ]
  display ; update the display
end 

to delete-nodes
  if mouse-down? [
    ask turtles with [distancexy mouse-xcor mouse-ycor < 2] [
      die
      display ; update the display
    ]
    stop
  ]
end