globals
[
  tick-delta                           ;; how much we advance the tick counter this time through
  max-tick-delta                       ;; the largest tick-delta is allowed to be
  box-edge                             ;; distance of box edge from axes
  left-particles right-particles       ;; particles in the left and right chambers
  avg-speed-cyan avg-energy-cyan       ;; left chamber averages
  avg-speed-magenta avg-energy-magenta ;; right chamber averages
  fast medium slow                     ;; current counts
  cyans magentas
]

breed [ particles particle ]
breed [ flashes flash ]

flashes-own [birthday]

particles-own
[
  speed mass energy          ;; particle info
  last-collision
  step-size
]


to setup
  clear-all
  set-default-shape particles "circle"
  set-default-shape flashes "square"
  set max-tick-delta 0.1073
  set box-edge (round (max-pxcor * box-size / 100) - 1)
  make-box
  make-particles
  update-variables
  reset-ticks
end

to update-variables
  set avg-speed-cyan      mean [speed] of cyans
  set avg-speed-magenta    mean [speed] of magentas
  set avg-energy-cyan     mean [energy] of cyans
  set avg-energy-magenta   mean [energy] of magentas
end

to go
  ask particles [set step-size speed * tick-delta]
  ask particles [bounce]
  ask particles [ move ]
  ask particles
  [ if collide? [check-for-collision] ]
  tick-advance tick-delta
  if floor ticks > floor (ticks - tick-delta)
  [
     update-variables
     update-plots
  ]
  calculate-tick-delta

  ask flashes with [ticks - birthday > 0.4]
    [ die ]
  display
end

to calculate-tick-delta
  ;; tick-delta is calculated in such way that even the fastest
  ;; particle will jump at most 1 patch length in a tick. As
  ;; particles jump (speed * tick-delta) at every tick, making
  ;; tick length the inverse of the speed of the fastest particle
  ;; (1/max speed) assures that. Having each particle advance at most
  ;; one patch-length is necessary for it not to "jump over" a wall.
  ifelse any? particles with [speed > 0]
    [ set tick-delta min list (1 / (ceiling max [speed] of particles)) max-tick-delta ]
    [ set tick-delta max-tick-delta ]
end

to bounce  ;; particle procedure
  ;; if we are already on a wall, no need for further checks
  if pcolor = yellow [stop]
  ;; get the coordinates of the patch we'll be on if we go forward 1
  let new-patch patch-ahead step-size
  let new-px [pxcor] of new-patch
  let new-py [pycor] of new-patch
  if [pcolor] of new-patch != yellow
    [ stop ]
  ;; if hitting left or right wall, reflect heading around x axis
  if abs new-px = box-edge [ set heading (- heading)]
  ;; if hitting top or bottom wall, reflect heading around y axis
  if abs new-py = box-edge  [ set heading (180 - heading) ]
  ;; if hitting partition, reflect heading around x axis unless near an opening
  if new-px = 0 [set heading ( - heading)
                if [pcolor] of patch-ahead step-size = yellow [set heading  (180 - heading)]]
 ;; create some flash turtles to show the bouncing particles
  ask patch new-px new-py
  [ sprout-flashes 1 [
      set color pcolor - 2
      set birthday ticks
    ]
  ]
end

to move  ;; particle procedure
  if patch-ahead (speed * tick-delta) != patch-here
    [ set last-collision nobody ]
  jump (speed * tick-delta)
end

to check-for-collision  ;; particle procedure
  ;; Here we impose a rule that collisions only take place when there
  ;; are exactly two particles per patch.  We do this because when the
  ;; student introduces new particles from the side, we want them to
  ;; form a uniform wavefront.
  ;;
  ;; Why do we want a uniform wavefront?  Because it is actually more
  ;; realistic.  (And also because the curriculum uses the uniform
  ;; wavefront to help teach the relationship between particle collisions,
  ;; wall hits, and pressure.)
  ;;
  ;; Why is it realistic to assume a uniform wavefront?  Because in reality,
  ;; whether a collision takes place would depend on the actual headings
  ;; of the particles, not merely on their proximity.  Since the particles
  ;; in the wavefront have identical speeds and near-identical headings,
  ;; in reality they would not collide.  So even though the two-particles
  ;; rule is not itself realistic, it produces a realistic result.  Also,
  ;; unless the number of particles is extremely large, it is very rare
  ;; for three or more particles to land on the same patch (for example,
  ;; with 400 particles it happens less than 1% of the time).  So imposing
  ;; this additional rule should have only a negligible effect on the
  ;; aggregate behavior of the system.
  ;;
  ;; Why does this rule produce a uniform wavefront?  The particles all
  ;; start out on the same patch, which means that without the only-two
  ;; rule, they would all start colliding with each other immediately,
  ;; resulting in much random variation of speeds and headings.  With
  ;; the only-two rule, they are prevented from colliding with each other
  ;; until they have spread out a lot.  (And in fact, if you observe
  ;; the wavefront closely, you will see that it is not completely smooth,
  ;; because some collisions eventually do start occurring when it thins out while fanning.)

  if count other particles-here = 1
  [
    ;; the following conditions are imposed on collision candidates:
    ;;   1. they must have a lower who number than my own, because collision
    ;;      code is asymmetrical: it must always happen from the point of view
    ;;      of just one particle.
    ;;   2. they must not be the same particle that we last collided with on
    ;;      this patch, so that we have a chance to leave the patch after we've
    ;;      collided with someone.
    let candidate one-of other particles-here with
      [who < [who] of myself and myself != last-collision]
    ;; we also only collide if one of us has non-zero speed. It's useless
    ;; (and incorrect, actually) for two particles with zero speed to collide.
    if (candidate != nobody) and (speed > 0 or [speed] of candidate > 0)
    [
      collide-with candidate
      set last-collision candidate
      ask candidate [ set last-collision myself ]
    ]
  ]
end

;; implements a collision with another particle.
;;
;; THIS IS THE HEART OF THE PARTICLE SIMULATION, AND YOU ARE STRONGLY ADVISED
;; NOT TO CHANGE IT UNLESS YOU REALLY UNDERSTAND WHAT YOU'RE DOING!
;;
;; The two particles colliding are self and other-particle, and while the
;; collision is performed from the point of view of self, both particles are
;; modified to reflect its effects. This is somewhat complicated, so I'll
;; give a general outline here:
;;   1. Do initial setup, and determine the heading between particle centers
;;      (call it theta).
;;   2. Convert the representation of the velocity of each particle from
;;      speed/heading to a theta-based vector whose first component is the
;;      particle's speed along theta, and whose second component is the speed
;;      perpendicular to theta.
;;   3. Modify the velocity vectors to reflect the effects of the collision.
;;      This involves:
;;        a. computing the velocity of the center of mass of the whole system
;;           along direction theta
;;        b. updating the along-theta components of the two velocity vectors.
;;   4. Convert from the theta-based vector representation of velocity back to
;;      the usual speed/heading representation for each particle.
;;   5. Perform final cleanup and update derived quantities.
to collide-with [ other-particle ] ;; particle procedure
  ;;; PHASE 1: initial setup

  ;; for convenience, grab some quantities from other-particle
  let mass2 [mass] of other-particle
  let speed2 [speed] of other-particle
  let heading2 [heading] of other-particle

  ;; since particles are modeled as zero-size points, theta isn't meaningfully
  ;; defined. we can assign it randomly without affecting the model's outcome.
  let theta (random-float 360)



  ;;; PHASE 2: convert velocities to theta-based vector representation

  ;; now convert my velocity from speed/heading representation to components
  ;; along theta and perpendicular to theta
  let v1t (speed * cos (theta - heading))
  let v1l (speed * sin (theta - heading))

  ;; do the same for other-particle
  let v2t (speed2 * cos (theta - heading2))
  let v2l (speed2 * sin (theta - heading2))



  ;;; PHASE 3: manipulate vectors to implement collision

  ;; compute the velocity of the system's center of mass along theta
  let vcm (((mass * v1t) + (mass2 * v2t)) / (mass + mass2) )

  ;; now compute the new velocity for each particle along direction theta.
  ;; velocity perpendicular to theta is unaffected by a collision along theta,
  ;; so the next two lines actually implement the collision itself, in the
  ;; sense that the effects of the collision are exactly the following changes
  ;; in particle velocity.
  set v1t (2 * vcm - v1t)
  set v2t (2 * vcm - v2t)



  ;;; PHASE 4: convert back to normal speed/heading

  ;; now convert my velocity vector into my new speed and heading
  set speed sqrt ((v1t ^ 2) + (v1l ^ 2))
  set energy (0.5 * mass * speed * speed)
  ;; if the magnitude of the velocity vector is 0, atan is undefined. but
  ;; speed will be 0, so heading is irrelevant anyway. therefore, in that
  ;; case we'll just leave it unmodified.
  if v1l != 0 or v1t != 0
    [ set heading (theta - (atan v1l v1t)) ]

  ;; and do the same for other-particle
  ask other-particle [
    set speed sqrt ((v2t ^ 2) + (v2l ^ 2))
    set energy (0.5 * mass * (speed ^ 2))
    if v2l != 0 or v2t != 0
      [ set heading (theta - (atan v2l v2t)) ]
  ]

  ;; PHASE 5: final updates

  ;; now recolor, since color is based on quantities that may have changed
  recolor
  ask other-particle
    [ recolor ]
end

to recolor  ;; particle procedure
  let values [ speed ] of breed
  let lower-limit mean values - 3 * standard-deviation values
  let upper-limit mean values + 3 * standard-deviation values
  set color scale-color color speed (lower-limit - 1) (upper-limit + 1)
end

;;;
;;; drawing procedures
;;;

;; draws the box
to make-box
  ask patches with [ ((abs pxcor = box-edge) and (abs pycor <= box-edge)) or
                     ((abs pycor = box-edge) and (abs pxcor <= box-edge)) or
                     ((abs pycor <= box-edge) and (pxcor = 0))]
    [ set pcolor yellow ]
end

to open-middle
  ask patches with [ pxcor = 0 and (abs pycor <= floor (box-edge * (opening-size / 100)))
                     and (abs pycor <= (box-edge - 1))] ;; in case opening reaches box edge
  [set pcolor black ask flashes-here [die]]
end


to close-middle
  ask patches with [ pxcor = 0 and (abs pycor <= box-edge) ]
    [ set pcolor yellow ]
end

;; creates initial particles
to make-particles
  create-particles num-cyans [
    set speed cyan-init-speed
    set mass cyan-mass
    random-position-left
    set color cyan
  ]
  create-particles num-magentas [
    set speed magenta-init-speed
    set mass magenta-mass
    random-position-right
    set shape "circle"
    set color magenta
  ]
  set cyans particles with [color = cyan]
  set magentas particles with [color = magenta]
  ask particles
  [
    set energy (0.5 * mass * speed * speed)
    ;; make their graphical size equal to the cube root of their mass
    set size  mass ^ .33
    set last-collision nobody
    recolor
  ]
  calculate-tick-delta
end


to random-position-left ;; particle procedure
  setxy ( 1 + random-float (box-edge - 2))
        ((1 - box-edge) + random-float (2 * box-edge - 2))
end

to random-position-right ;; particle procedure
  setxy ((1 - box-edge) + random-float (box-edge - 2))
        ((1 - box-edge) + random-float (2 * box-edge - 2))
end


;;; plotting procedures
to-report max-init-speed
  report (max (list cyan-init-speed magenta-init-speed))
end

to-report max-particle-mass
  report (max (list cyan-mass magenta-mass))
end


; Copyright 1997 Uri Wilensky.
; See Info tab for full copyright and license.
@#$#@#$#@
GRAPHICS-WINDOW
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45
4.0
1
10
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ticks
30.0

BUTTON
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43
93
76
go/stop
go
T
1
T
OBSERVER
NIL
NIL
NIL
NIL
0

BUTTON
7
10
93
43
NIL
setup
NIL
1
T
OBSERVER
NIL
NIL
NIL
NIL
1

SWITCH
96
44
199
77
collide?
collide?
0
1
-1000

PLOT
356
416
626
594
Average Speeds
time
speed
0.0
20.0
0.0
15.0
true
true
"set-plot-y-range 0 (1.5 * max-init-speed)" ""
PENS
"cyan" 1.0 0 -11221820 true "" "plotxy ticks avg-speed-cyan"
"magenta" 1.0 0 -5825686 true "" "plotxy ticks avg-speed-magenta"

PLOT
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414
895
594
Average Energies
time
energy
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20.0
0.0
750.0
true
true
"set-plot-y-range 0 (1.5 * max-init-speed * max-init-speed * max-particle-mass)" ""
PENS
"cyan" 1.0 0 -11221820 true "" "plotxy ticks avg-energy-cyan"
"magenta" 1.0 0 -5825686 true "" "plotxy ticks avg-energy-magenta"

SLIDER
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162
opening-size
opening-size
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99
30
1
1
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HORIZONTAL

BUTTON
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290
43
open
open-middle
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1
T
OBSERVER
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NIL
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BUTTON
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290
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close
close-middle
NIL
1
T
OBSERVER
NIL
NIL
NIL
NIL
0

SLIDER
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225
339
258
num-cyans
num-cyans
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500
217
1
1
NIL
HORIZONTAL

SLIDER
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224
169
257
num-magentas
num-magentas
2
500
100
1
1
NIL
HORIZONTAL

SLIDER
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cyan-init-speed
cyan-init-speed
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50
20
1
1
NIL
HORIZONTAL

SLIDER
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169
295
magenta-init-speed
magenta-init-speed
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1
1
NIL
HORIZONTAL

SLIDER
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cyan-mass
cyan-mass
1
50
23
1
1
NIL
HORIZONTAL

SLIDER
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magenta-mass
magenta-mass
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2
1
1
NIL
HORIZONTAL

SLIDER
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box-size
box-size
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1
1
%
HORIZONTAL

MONITOR
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376
169
421
magentas in left chamber
count magentas with [ xcor < 0 ]
3
1
11

MONITOR
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cyans in right chamber
count cyans with [ xcor > 0 ]
0
1
11

MONITOR
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average speed magenta
avg-speed-magenta
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11

MONITOR
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average speed cyan
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11

MONITOR
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average energy magenta
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11

MONITOR
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average energy cyan
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TEXTBOX
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Magenta Gas Settings
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TEXTBOX
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Cyan Gas Settings
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MONITOR
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max particle speed
max [speed] of particles
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11

@#$#@#$#@
## WHAT IS IT?

This model is one in a series of GasLab models. They use the same basic rules for simulating the behavior of gases.  Each model integrates different features in order to highlight different aspects of gas behavior.

The basic principle of the models is that gas particles are assumed to have two elementary actions: they move and they collide --- either with other particles or with any other objects such as walls.

This model simulates the behavior of two different types of gas particles in a box with a partitioning wall. Part or all of the wall can be removed, allowing the particles to mix together. It was one of the original CM StarLogo applications (under the name GPCEE) and is now ported to NetLogo as part of the Connected Mathematics "Making Sense of Complex Phenomena" Modeling Project.

This model is part of the Connected Mathematics "Making Sense of Complex Phenomena" Modeling Project.

## HOW IT WORKS

The particles are modeled as hard balls with no internal energy except that which is due to their motion.  Collisions between particles are elastic.  Particles are colored according to speed --- blue for slow, green for medium, and red for high speeds.

Coloring of the particles is with respect to one speed (10). Particles with a speed less than 5 are blue, ones that are more than 15 are red, while all in those in-between are green.

The exact way two particles collide is as follows:  
1. A particle moves in a straight line without changing its speed, unless it collides with another particle or bounces off the wall.  
2. Two particles "collide" if they find themselves on the same patch.  
3. A random axis is chosen, as if they are two balls that hit each other and this axis is the line connecting their centers.  
4. They exchange momentum and energy along that axis, according to the conservation of momentum and energy.  This calculation is done in the center of mass system.  
5. Each particle is assigned its new velocity, energy, and heading.  
6. If a particle finds itself on or very close to a wall of the container, it "bounces" --- that is, reflects its direction and keeps its same speed.

## HOW TO USE IT

Initial settings:  
- BOX-SIZE: the percent of the width and height of the world that the box will occupy.  
- NUM-MAGENTAS and NUM-CYAN: the number of gas particles of each color.  
- MAGENTA-INIT-SPEED and CYAN-INIT-SPEED: the initial speed the the respective particle.  
- MAGENTA-MASS and CYAN-MASS: the mass of the respective particles.

The SETUP button will set these initial conditions.  
The GO button will begin the simulation.

Controls:  
The OPEN button opens the wall between the chambers of the box.  
The CLOSE button closes the wall between the chambers of the box.

Other settings:  
- COLLIDE?: Turns collisions between particles on and off.  
- OPENING-SIZE: the size of the opening made as a percentage of the BOX-SIZE when the OPEN button is pressed.

Monitors:  
- MAGENTAS IN RIGHT CHAMBER: number of magenta particles in the right chamber.  
- CYANS IN LEFT CHAMBER: number of cyan particles in the left chamber  
- AVERAGE ENERGY MAGENTA or CYAN: average energy of magenta or cyan particles.  
- AVERAGE SPEED MAGENTA or CYAN: average speed of magenta or cyan particles.

Plots:  
- AVERAGE ENERGY: average energy of the different particles over time.  
- AVERAGE SPEED: average speed of the different particles over time.

## THINGS TO NOTICE

What variables affect how quickly the model reaches a new equilibrium when the wall is removed?

Why does the average speed for each color decrease as the model runs with the wall in place, even though the average energy remains constant?

What happens to the relative energies and speeds of each kind of particle as they intermingle?   What effect do the initial speeds and masses have on this relationship?

Does the system reach an equilibrium state?

Do heavier particles tend to have higher or lower speeds when the distribution of energy has reached equilibrium?

Is it reasonable that this box can be considered to be "insulated"?

## THINGS TO TRY

Calculate how long the model takes to reach equilibrium with different sizes of windows (holding other parameters constant).

Calculate how long the model takes to reach equilibrium with different particle speeds.

Set the number of cyan particles to zero.  This is a model of a gas expanding into a vacuum.  This experiment was first done by Joule, using two insulated chambers separated by a valve.  He found that the temperature of the gas remained the same when the valve was opened.  Why would this be true? Is this model consistent with that observation?

Try some extreme situations, to test your intuitive understanding:  
-- masses the same, speeds of the two particles very different.  
-- speeds the same, masses very different.  
-- a very small number of one kind of particle -- almost, but not quite a vacuum.  What happens to those few particles, and how do they affect the other kind?

Try relating quantitatively the ratio of the equilibrium speeds of both gases after the wall is opened to the ratio of the masses of both gases.  How are they related?

## EXTENDING THE MODEL

Monitor pressure in the right and left chambers.

Monitor temperature in the right and left chambers.

Replace the partition wall with a moveable piston, so that the two kinds of particles can push against each other without intermingling.  Do they arrive at a different equilibrium then?

Replace the partition wall with a surface that can transmit energy.

Add the histograms of energy and speed distribution (such as found in the "Free Gas" model).

## NETLOGO FEATURES

Notice how collisions are detected by the turtles and how the code guarantees that the same two particles do not collide twice.  What happens if we let the patches detect them?

## CREDITS AND REFERENCES

This model was developed as part of the GasLab curriculum (http://ccl.northwestern.edu/curriculum/gaslab/) and has also been incorporated into the Connected Chemistry curriculum (http://ccl.northwestern.edu/curriculum/ConnectedChemistry/)


## HOW TO CITE

If you mention this model in a publication, we ask that you include these citations for the model itself and for the NetLogo software:

* Wilensky, U. (1997).  NetLogo GasLab Two Gas model.  http://ccl.northwestern.edu/netlogo/models/GasLabTwoGas.  Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.
* Wilensky, U. (1999). NetLogo. http://ccl.northwestern.edu/netlogo/. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.

## COPYRIGHT AND LICENSE

Copyright 1997 Uri Wilensky.

![CC BY-NC-SA 3.0](http://i.creativecommons.org/l/by-nc-sa/3.0/88x31.png)

This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License.  To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/ or send a letter to Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA.

Commercial licenses are also available. To inquire about commercial licenses, please contact Uri Wilensky at uri@northwestern.edu.

This model was created as part of the project: CONNECTED MATHEMATICS: MAKING SENSE OF COMPLEX PHENOMENA THROUGH BUILDING OBJECT-BASED PARALLEL MODELS (OBPML).  The project gratefully acknowledges the support of the National Science Foundation (Applications of Advanced Technologies Program) -- grant numbers RED #9552950 and REC #9632612.

This model was converted to NetLogo as part of the projects: PARTICIPATORY SIMULATIONS: NETWORK-BASED DESIGN FOR SYSTEMS LEARNING IN CLASSROOMS and/or INTEGRATED SIMULATION AND MODELING ENVIRONMENT. The project gratefully acknowledges the support of the National Science Foundation (REPP & ROLE programs) -- grant numbers REC #9814682 and REC-0126227. Converted from StarLogoT to NetLogo, 2002.

@#$#@#$#@
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Circle -16777216 true false 180 75 60
Polygon -16777216 true false 150 168 90 184 62 210 47 232 67 244 90 220 109 205 150 198 192 205 210 220 227 242 251 229 236 206 212 183

fish
false
0
Polygon -1 true false 44 131 21 87 15 86 0 120 15 150 0 180 13 214 20 212 45 166
Polygon -1 true false 135 195 119 235 95 218 76 210 46 204 60 165
Polygon -1 true false 75 45 83 77 71 103 86 114 166 78 135 60
Polygon -7500403 true true 30 136 151 77 226 81 280 119 292 146 292 160 287 170 270 195 195 210 151 212 30 166
Circle -16777216 true false 215 106 30

flag
false
0
Rectangle -7500403 true true 60 15 75 300
Polygon -7500403 true true 90 150 270 90 90 30
Line -7500403 true 75 135 90 135
Line -7500403 true 75 45 90 45

flower
false
0
Polygon -10899396 true false 135 120 165 165 180 210 180 240 150 300 165 300 195 240 195 195 165 135
Circle -7500403 true true 85 132 38
Circle -7500403 true true 130 147 38
Circle -7500403 true true 192 85 38
Circle -7500403 true true 85 40 38
Circle -7500403 true true 177 40 38
Circle -7500403 true true 177 132 38
Circle -7500403 true true 70 85 38
Circle -7500403 true true 130 25 38
Circle -7500403 true true 96 51 108
Circle -16777216 true false 113 68 74
Polygon -10899396 true false 189 233 219 188 249 173 279 188 234 218
Polygon -10899396 true false 180 255 150 210 105 210 75 240 135 240

house
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0
Rectangle -7500403 true true 45 120 255 285
Rectangle -16777216 true false 120 210 180 285
Polygon -7500403 true true 15 120 150 15 285 120
Line -16777216 false 30 120 270 120

leaf
false
0
Polygon -7500403 true true 150 210 135 195 120 210 60 210 30 195 60 180 60 165 15 135 30 120 15 105 40 104 45 90 60 90 90 105 105 120 120 120 105 60 120 60 135 30 150 15 165 30 180 60 195 60 180 120 195 120 210 105 240 90 255 90 263 104 285 105 270 120 285 135 240 165 240 180 270 195 240 210 180 210 165 195
Polygon -7500403 true true 135 195 135 240 120 255 105 255 105 285 135 285 165 240 165 195

line
true
0
Line -7500403 true 150 0 150 300

line half
true
0
Line -7500403 true 150 0 150 150

pentagon
false
0
Polygon -7500403 true true 150 15 15 120 60 285 240 285 285 120

person
false
0
Circle -7500403 true true 110 5 80
Polygon -7500403 true true 105 90 120 195 90 285 105 300 135 300 150 225 165 300 195 300 210 285 180 195 195 90
Rectangle -7500403 true true 127 79 172 94
Polygon -7500403 true true 195 90 240 150 225 180 165 105
Polygon -7500403 true true 105 90 60 150 75 180 135 105

plant
false
0
Rectangle -7500403 true true 135 90 165 300
Polygon -7500403 true true 135 255 90 210 45 195 75 255 135 285
Polygon -7500403 true true 165 255 210 210 255 195 225 255 165 285
Polygon -7500403 true true 135 180 90 135 45 120 75 180 135 210
Polygon -7500403 true true 165 180 165 210 225 180 255 120 210 135
Polygon -7500403 true true 135 105 90 60 45 45 75 105 135 135
Polygon -7500403 true true 165 105 165 135 225 105 255 45 210 60
Polygon -7500403 true true 135 90 120 45 150 15 180 45 165 90

square
false
0
Rectangle -7500403 true true 30 30 270 270

square 2
false
0
Rectangle -7500403 true true 30 30 270 270
Rectangle -16777216 true false 60 60 240 240

star
false
0
Polygon -7500403 true true 151 1 185 108 298 108 207 175 242 282 151 216 59 282 94 175 3 108 116 108

target
false
0
Circle -7500403 true true 0 0 300
Circle -16777216 true false 30 30 240
Circle -7500403 true true 60 60 180
Circle -16777216 true false 90 90 120
Circle -7500403 true true 120 120 60

tree
false
0
Circle -7500403 true true 118 3 94
Rectangle -6459832 true false 120 195 180 300
Circle -7500403 true true 65 21 108
Circle -7500403 true true 116 41 127
Circle -7500403 true true 45 90 120
Circle -7500403 true true 104 74 152

triangle
false
0
Polygon -7500403 true true 150 30 15 255 285 255

triangle 2
false
0
Polygon -7500403 true true 150 30 15 255 285 255
Polygon -16777216 true false 151 99 225 223 75 224

truck
false
0
Rectangle -7500403 true true 4 45 195 187
Polygon -7500403 true true 296 193 296 150 259 134 244 104 208 104 207 194
Rectangle -1 true false 195 60 195 105
Polygon -16777216 true false 238 112 252 141 219 141 218 112
Circle -16777216 true false 234 174 42
Rectangle -7500403 true true 181 185 214 194
Circle -16777216 true false 144 174 42
Circle -16777216 true false 24 174 42
Circle -7500403 false true 24 174 42
Circle -7500403 false true 144 174 42
Circle -7500403 false true 234 174 42

turtle
true
0
Polygon -10899396 true false 215 204 240 233 246 254 228 266 215 252 193 210
Polygon -10899396 true false 195 90 225 75 245 75 260 89 269 108 261 124 240 105 225 105 210 105
Polygon -10899396 true false 105 90 75 75 55 75 40 89 31 108 39 124 60 105 75 105 90 105
Polygon -10899396 true false 132 85 134 64 107 51 108 17 150 2 192 18 192 52 169 65 172 87
Polygon -10899396 true false 85 204 60 233 54 254 72 266 85 252 107 210
Polygon -7500403 true true 119 75 179 75 209 101 224 135 220 225 175 261 128 261 81 224 74 135 88 99

wheel
false
0
Circle -7500403 true true 3 3 294
Circle -16777216 true false 30 30 240
Line -7500403 true 150 285 150 15
Line -7500403 true 15 150 285 150
Circle -7500403 true true 120 120 60
Line -7500403 true 216 40 79 269
Line -7500403 true 40 84 269 221
Line -7500403 true 40 216 269 79
Line -7500403 true 84 40 221 269

x
false
0
Polygon -7500403 true true 270 75 225 30 30 225 75 270
Polygon -7500403 true true 30 75 75 30 270 225 225 270

@#$#@#$#@
NetLogo 5.1.0
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@#$#@#$#@
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@#$#@#$#@
default
0.0
-0.2 0 0.0 1.0
0.0 1 1.0 0.0
0.2 0 0.0 1.0
link direction
true
0
Line -7500403 true 150 150 90 180
Line -7500403 true 150 150 210 180

@#$#@#$#@
0
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