Felling (2x2)

-- 0.5

local isBlock = true
local totalBlocks = 0
local onGround = true

function fuelCheck()
    fuelLevel = turtle.getFuelLevel()
    print("Checking fuel before start...")
    os.sleep(0.5)
    if fuelLevel < 100 then
        os.error("Insufficient fuel in tank.")
    else
        print("Sufficient fuel in tank.")
    end
end

function init()
    fuelCheck()

    turtle.dig()
    turtle.forward()
end

function fellTree()
    onGround = true
    isBlock = true

    while isBlock or totalBlocks < 5 do
        totalBlocks = totalBlocks + 1
        isBlock = turtle.detectUp()
        turtle.digUp()
        turtle.up()
    end

    if not isBlock then
        repeat
            turtle.down()
            onGround = turtle.detectDown()
        until onGround
    end
end

function moveNext()
    turtle.dig()
    turtle.forward()
    turtle.turnRight()
end

init()

for i = 0, 3, 1 do
    fellTree()
    moveNext()
end

print("Total blocks felled/moved: " .. totalBlocks)