flowchart TB
  H[基地] --- A[低风险补给点]
  H --- B[教学废墟]
  A --- C[村庄/交易点]
  B --- D[城市废墟]
  C --- E[森林边缘]
  D --- F[地铁入口]
  E --- G[避难所外围]
  F --- G