digraph {
    node [shape = "box", style = "filled, rounded"]

    subgraph clustermain {
        label = "main"

        node [color = limegreen]

        main3[label = "..."]
        main2[label = "..."]
        main1[label = "..."]

        main3 -> main2 -> main1
    }

    subgraph clusterplayground {
        label = "playground"

        node [color = orchid]

        playground2[label = "visualization"]
        playground1[label = "methods"]

        playground2 -> playground1
    }

    playground1 -> main2
}