Langton's ant. LRRL. Symmetrical.

stor = tpt.el["stor"].id
dlay = tpt.el["dlay"].id
psns = tpt.el["psns"].id
tsns = tpt.el["tsns"].id

local ANT3 = elements.allocate("DayLightInc", "ANT3")
elements.element(ANT3, elements.element(elements.DEFAULT_PT_PROT))
elements.property(ANT3, "Name", "ANT3")
elements.property(ANT3, "Description", "Langtons's ant. You can set speed by changing ''dcolour'' property (Default = 20). LRRL. stor-dlay-psns-tsns")
elements.property(ANT3, "Colour", 0x0091d7)
elements.property(ANT3, "MenuSection", 12)

local function update (i,xu,yu,s,nt)
  ctype = sim.partProperty(i, "ctype")
  if ctype == 0 then
    sim.partProperty(i, "life", xu);
    sim.partProperty(i, "tmp2", yu);
    sim.partProperty(i,"ctype",14);
    dc = sim.partProperty
    if dc(i,"dcolour") == 0 then dc(i, "dcolour", 20) end
    sim.partProperty(i, "tmp", 3)
    sim.partProperty(i, "x", 5)
    sim.partProperty(i, "y", 5)
  else

  for ir = 1,sim.partProperty(i,"dcolour"),1 do
  oldX = sim.partProperty(i, "life") -- get x
  oldY = sim.partProperty(i, "tmp2") -- get y

  side = sim.partProperty(i,"tmp")
  sim.partProperty(i, "x", 5)
  sim.partProperty(i, "y", 5)

  idr = sim.partCreate(-1,oldX,oldY, tpt.el["dmnd"].id)
  if idr == -1 then
    id = sim.partID(oldX,oldY)
  else
    id = nil
    sim.partKill(idr)
  end

  if id == nil then
      side = (side-1)%4
      sim.partCreate(-3,oldX,oldY,stor) --if empty
  else
      if dc(id, "type") == stor then
           side = (side-1)%4
           dc(id, "type", dlay)
           elseif dc(id, "type") == dlay then
                 side = (side+1)%4
                 dc(id,"type",psns)
                 elseif dc(id, "type") == psns then
                     side = (side+1)%4
                     dc(id,"type",tsns)
                     elseif dc(id, "type") == tsns then
                          side = (side-1)%4
                          dc(id,"type",stor)
      end --if not empty
  end

  if side == 0 then --up
      oldY = oldY - 1
      elseif side == 1 then --right
          oldX = oldX+1
          elseif side == 2 then --down
              oldY = oldY+1
              elseif side == 3 then --left
              oldX = oldX-1
  end


  sim.partProperty(i, "life", oldX)
  sim.partProperty(i,"tmp2", oldY) --return particle
  sim.partProperty(i, "tmp", side)
  end
  end
end
elements.property(ANT3, "Update", update)