Factorio: Cheap and tileable death-world wall defense

Add roboports and this should last you forever. :) My most resource efficient wall defense yet. Only seems to take damage if multiple large-scale full-evolution attacks happen at the same time and in the same place. (That and spitters of course. Spitters will always damage your walls) Q: Why didn’t you use 2 wide gaps in your dragon’s teeth? A: All designs I’ve tried with 2 wide gaps end up needing over twice the ammount of walls, turrets, and ground space to put up the same defense -- and dont slow the enemy down to anything even comparable to 1 wide gap designs. On top of this, they dont seem to take much less damage due to the nature of spitters.