(function()
    for n=1,size do
        for m=1,size-1 do
            if not tryForwards() then return end
        end
        if n<size then
            local turn = (math.fmod(n,2) == 0) and turnLeft or turnRight
            turn()
            if not tryForwards() then return end
            turn()
        end
    end
end)()