exam

globals [
  plastic-speed
  turtle-speed
]

breed [sea-turtles sea-turtle]
breed [plastics plastic]
breed [foods food]

sea-turtles-own [
  body-condition
  plastic-eaten
  plastic-mass-ingested
  food-eaten
  speed
  scl ; straight carapace length in cm
]

plastics-own [
  mass
]

to setup
  clear-all
  set plastic-speed 0.02
  set turtle-speed (1.4 / 3.6)
  set plastic-ingestion-chance 0.3 ; you can adjust this
  set food-ingestion-chance 0.6 ; you can adjust this
  ask patches [ set pcolor sky ] ; light blue background

  create-sea-turtles 100 [
    set shape "turtle"
    set color green
    set size 2
    set body-condition "excellent"
    set plastic-eaten 0
    set plastic-mass-ingested 0
    set food-eaten 0
    set speed turtle-speed
    set scl random-float 50 + 30 ; SCL range 30–80 cm
    setxy random-xcor random-ycor
  ]

  create-plastics 100 [
    set shape "circle"
    set size 0.5
    set color pink
    set mass random-float 69 + 1 ; mass from 1 to 70g
    setxy random-xcor random-ycor
  ]

  create-foods 50 [
    set shape "dot"
    set size 0.4
    set color green + 2
    setxy random-xcor random-ycor
  ]

  reset-ticks
end 

to go
  add-plastics
  add-foods
  ask sea-turtles [
    forage
    avoid-collisions
    eat-plastic
    eat-food
    update-condition
    update-health-distribution

  ]
  tick
end 

to add-plastics
  if count plastics < 200 [
    create-plastics 2 [
      set shape "circle"
      set size 0.5
      set color pink
      set mass random-float 69 + 1
      setxy random-xcor random-ycor
    ]
  ]
end 

to add-foods
  if count foods < 100 [
    create-foods 1 [
      set shape "dot"
      set size 0.5
      set color grey + 2
      setxy random-xcor random-ycor
    ]
  ]
end 

to avoid-collisions
  let nearby-turtle one-of other turtles in-radius 1.5
  if nearby-turtle != nobody [
    right random 180
    forward 0.5
  ]
end 

to update-health-distribution
  set-current-plot "Turtle Health Distribution"
  clear-plot
  let conditions ["excellent" "good" "fair" "poor" "dead"]
  foreach conditions [
    condition ->
    set-current-plot-pen condition
    plot count sea-turtles with [body-condition = condition]
  ]
end 

to eat-plastic
  let target one-of plastics with [distance myself < 1]
  if target != nobody and random-float 1 < plastic-ingestion-chance [
    set plastic-eaten plastic-eaten + 1
    set plastic-mass-ingested plastic-mass-ingested + [mass] of target
    ask target [ die ]
  ]
end 

to eat-food
  let target one-of foods with [distance myself < 1]
  if target != nobody and random-float 1 < food-ingestion-chance [
    set food-eaten food-eaten + 1
    ask target [ die ]
  ]
end 

to forage
  let decision random-float 1

  ; Decide whether to search for food or plastic
  if decision < food-ingestion-chance [
    let target one-of foods in-radius 10
    if target != nobody [
      face target
      fd speed * 0.2
    ]
    if target = nobody [
      rt random 360
      fd speed * 0.1
    ]
  ]
  if decision >= food-ingestion-chance [
    let target one-of plastics in-radius 10
    if target != nobody [
      face target
      fd speed * 0.2
    ]
    if target = nobody [
      rt random 360
      fd speed * 0.1
    ]
  ]
end 

to update-condition
  let plastic-per-scl plastic-mass-ingested / scl

  ; Check for body condition
  if plastic-per-scl <= 0.0718 [
    set body-condition "excellent"
    set color green
    set speed turtle-speed
  ]
  if plastic-per-scl > 0.0718 and plastic-per-scl <= 0.1460 [
    set body-condition "good"
    set color violet
    set speed turtle-speed * 0.75
  ]
  if plastic-per-scl > 0.1460 and plastic-per-scl <= 0.2282 [
    set body-condition "fair"
    set color yellow
    set speed turtle-speed * 0.5
  ]
  if plastic-per-scl > 0.2282 and plastic-per-scl <= 0.30 [
    set body-condition "poor"
    set color red
    set speed turtle-speed * 0.25
  ]
  if plastic-per-scl > 0.30 [
    set body-condition "dead"
    set color black ; Turtle dies
    die
  ]
end