With a Supply Depot wall up, a Marine or Reaper can sit safely behind the wall and kill off any early Zerglings that may attack. Adding a Barracks and 2 Supply Depots to wall off the ramp is a basic Terran vs Zerg strategy. To protect against Zerglings, players simply have to wall off their ramp with buildings. 3 How long does it take to get good at Starcraft 2?.
