Generated by XState Viz: https://xstate.js.org/viz

machine.js

const addNumber = assign({
  numbers: (ctx, event) => {
    let { howMany = 5 } = event;
    let toAdd = [];

    for (let i = 0; i < howMany; i++) {
      toAdd.push(Math.floor(Math.random() * 9));
    }

    return [...ctx.numbers, ...toAdd];
  },
});

// Guard game over
function isGameOver(context) {
  return context.numbers.length >= 20;
}

const gameMachine = Machine(
  {
    initial: "start",
    context: { numbers: [] },
    states: {
      start: {
        on: {
          ADD_NUMBER: {
            target: "playing",
            actions: "addNumber",
          },
        },
      },
      playing: {
        always: {
          target: "gameover",
          cond: "isGameOver",
        },
        on: {
          ADD_NUMBER: {
            target: "playing",
            actions: "addNumber",
          },
        },
      },
      gameover: {},
    },
  },
  { actions: { addNumber }, guards: { isGameOver } }
);