3x3 digging

-- 0.4 3x3

local x = 15
local fuelLevelStart = turtle.getFuelLevel()
local fuelUsed = 100

function dig()
    turtle.turnRight()
    turtle.dig()
    turtle.digDown()
    turtle.down()
    turtle.dig()
    turtle.turnLeft()
    turtle.turnLeft()
    turtle.dig()
    turtle.up()
    turtle.dig()
    turtle.digUp()
    turtle.up()
    turtle.dig()
    turtle.turnRight()
    turtle.turnRight()
    turtle.dig()
    turtle.turnLeft()
    turtle.down()
end

function torch()
    turtle.select(16)
    turtle.placeDown()
    turtle.select(1)
end

if fuelLevelStart < fuelUsed then error("Insufficient fuel") end

for i = 1, x, 1 do
    turtle.dig()
    turtle.forward()
    dig()

    if i == 4 then torch() end
    if i == 12 then torch() end
end

for i = 1, x, 1 do
    turtle.back()
end

print("Finished! Total fuel used: " .. fuelLevelStart - turtle.getFuelLevel())