digraph {

        start [label="Wormhole Code\nMachine" style="dotted"]
        {rank=same; start S0}
        {rank=same; P_list_nameplates P_allocate}
        {rank=same; S1 S2}
        {rank=same; S3 P_allocate_generate}
        start -> S0 [style="invis"]
        S0 [label="S0:\nunknown"]
        S0 -> P_set_code [label="set"]
        P_set_code [shape="box" label="W.set_code"]
        P_set_code -> S_known
        S_known [label="known" color="green"]

        S0 -> P_list_nameplates [label="input"]
        S2 [label="S2: typing\nnameplate"]

        S2 -> P_nameplate_completion [label="<tab>"]
        P_nameplate_completion [shape="box" label="do completion"]
        P_nameplate_completion -> P_list_nameplates
        P_list_nameplates [shape="box" label="NL.refresh_nameplates"]
        P_list_nameplates -> S2

        S2 -> P_got_nameplates [label="got_nameplates"]
        P_got_nameplates [shape="box" label="stash nameplates\nfor completion"]
        P_got_nameplates -> S2
        S2 -> P_finish_nameplate [label="<return>"
                                                  color="orange"
                                                  fontcolor="orange"]
        P_finish_nameplate [shape="box" label="lookup wordlist\nfor completion"]
        P_finish_nameplate -> S3
        S3 [label="S3: typing\ncode"]
        S3 -> P_code_completion [label="<tab>"]
        P_code_completion [shape="box" label="do completion"]
        P_code_completion -> S3

        S3 -> P_set_code [label="<return>"
                                     color="orange" fontcolor="orange"]

        S0 -> P_allocate [label="allocate"]
        P_allocate [shape="box" label="C.tx_allocate"]
        P_allocate -> S1
        S1 [label="S1:\nallocating"]
        S1 -> P_allocate_generate [label="rx_allocated"]
        P_allocate_generate [shape="box" label="generate\nrandom code"]
        P_allocate_generate -> P_set_code
        
}