treeFarm

local xSize = 10
local ySize = 10

local xPos = 0
local yPos = 0
local zPos = 0

local minFuel = 20

local forward = true

function refuel()
  if turtle.getFuelLevel() < minFuel then
    turtle.select(16)
    turtle.refuel()
  end
end

function move()
  if turtle.detect() then
    return false
  end

  turtle.forward()
  if forward then
    yPos = yPos + 1
    if yPos > ySize then
      turtle.turnRight()
      turtle.forward()
      turtle.forward()
      turtle.turnRight()
      xPos = xPos + 1
      forward = not forward
    end
  else
    yPos = yPos - 1
    if yPos <= 0 then
      turtle.turnLeft()
      turtle.forward()
      turtle.forward()
      turtle.turnLeft()
      xPos = xPos + 1
      foward = not forward
    end
  end

  if xPos > xSize then
    if yPos == 0 then
      turtle.turnLeft()
    else
      while yPos > 0 do
        turtle.forward()
        yPos = yPos - 1
      end
    end

    while xPos > 0 do
      turtle.forward()
      turtle.forward()
      xPos = xPos - 1
    end
  end
end

function dig()
  turtle.dig()
end

while true do
  refuel()
  print(move())
  dig()
end