digraph G {
  rankdir=LR;
  nodesep=0.5;
  fontsize=11;

  node [shape="ellipse", style="filled"];

  {
    node [fillcolor="cyan"];
    b1_0 [label="base-0"];
    b1_1 [label="patch-1"];
    b1_2 [label="patch-2"];
    b1_3 [label="patch-3"];
  }

  b1_0 -> b1_1 -> b1_2 -> b1_3;
}