mine

local step = 0
local rows = 0
local turn = 1

function fwr()
while not turtle.forward() do
turtle.dig()
end
end

function turns()
if rows > 20 then
return
elseif turn == 1 then
turtle.turnLeft()
fwr()
turtle.turnLeft()
turn = 2
rows = rows + 1
forwarddig()
else
turtle.turnRight()
fwr()
turtle.turnRight()
turn = 1
rows = rows + 1
forwarddig()
end
end

function forwarddig()
    step = 0
        while step <= 20 do
            turtle.dig()
            turtle.digUp()
            turtle.digDown()
            fwr()
            step = step + 1
        end
    turns()
end

function Exit()
return
end

print("starting")
forwarddig()