local function digBlocks(blocks)
    for i = 1, blocks do
        turtle.dig()
        turtle.forward()
    end
end

local function digLayers(length, width, depth)
    length = length - 1
    local turnDirection = "right"

    for i = 1, depth do
        print(i ..  '/' .. depth .. " layers")

        for j = 1, width do
            digBlocks(length)

            if turnDirection == "right" and j < width then
                turtle.turnRight()
                turtle.dig()
                turtle.forward()
                turtle.turnRight()
                turnDirection = "left"
            elseif turnDirection == "left" and j < width then
                turtle.turnLeft()
                turtle.dig()
                turtle.forward()
                turtle.turnLeft()
                turnDirection = "right"
            end
        end

        if i < depth then
            turtle.turnRight()
            turtle.turnRight()
            turtle.digDown()
            turtle.down()
        end
    end
end

local function main()
    digLayers(3, 3, 6)
end

main()