-- save as: follow
rednet.open("left")
local fuelSlot = 16

local function fuel()
  if turtle.getFuelLevel() ~= "unlimited" and turtle.getFuelLevel() < 200 then
    turtle.select(fuelSlot)
    turtle.refuel(1)
  end
end

while true do
  local id, msg = rednet.receive()
  fuel()

  if msg == "f" then turtle.forward()
  elseif msg == "u" then turtle.up()
  elseif msg == "d" then turtle.down()
  elseif msg == "l" then turtle.turnLeft()
  elseif msg == "r" then turtle.turnRight()
  end

  rednet.send(id, "ok")
end
