PROGRAM CRASH

os.loadAPI("ocs/apis/sensor")

local sensor = sensor.wrap("left")
local glass = peripheral.wrap("right")

local wx, wy = -8.5, -8.5 -- world x/y
local x, y = 5, 5
local w, h = 60, 60
local bw, bh = w/20, h/20 -- block w/h

glass.clear()

local grassbox = glass.addBox(x, y, w, h, 0x32C82D, 1)
grassbox.setZIndex(0)
local building = glass.addBox(x+(bw*3), y+(bh*3), w-(bw*6), h-(bh*6), 0x999999, 1)
building.setZIndex(1)
local z = 2

local dont_add = {
  "Chicken%d+",
  "Cow%d+",
  "Sheep%d+",
  "Pig%d+",

  "Zombie%d+",
  "Skeleton%d+",
  "Spider%d+",
  "Creeper%d+",
  "Enderman%d+",
  "Bat%d+",
  "Witch%d+",
}

local players = {}

while true do
  local targets = sensor.getTargets()
  for i, v in pairs(targets) do
    local add = true
    for k,l in pairs(dont_add) do
      if string.find(i, l) then
        add = false
      end
    end
    if add then
      if not players[i] then
        players[i] = {}
        print("Added player: "..i)
      end
      if not players[i].box then
        players[i].box = glass.addBox(0, 0, 4, 4, 0xFF0000, 1)
        players[i].box.setZIndex(z)
        players[i].text = glass.addText(0, 0, i, 0x000000)
        players[i].text.setZIndex(z+1)
        z = z + 2
      end
      players[i].box.setX((v.Position.X - wx - 2 + x)*bw)
      players[i].box.setY((v.Position.Z - wy - 2 + y)*bh)
      players[i].text.setX((v.Position.X - wx + 3 + x)*bw)
      players[i].text.setY((v.Position.Z - wy - 2 + y)*bh)

      print("Player "..i.."'s box at ("..players[i].box.getX()..", "..players[i].box.getY()..")")
    end
  end
  for i,v in pairs(players) do
    if not targets[i] then
      if v.box then
        v.box.delete()
        v.box = nil
      end
      if v.text then
        v.text.delete()
        v.text = nil
      end
    end
  end
  sleep(0.1)
end