particles/Main.cs

using Godot;
using System;
using Particles.ParticleSimulation;

public class Main : Node
{

    public int Seed;
    private int _nParticles;
    
    public void StartSimulation(int nParticles)
    {
        _nParticles = nParticles;
        var particleSimulationPackedScene = GD.Load<PackedScene>("res://ParticleSimulation/ParticleSimulationScene.tscn");
        var particleSimulationScene = particleSimulationPackedScene.Instance<ParticleSimulationScene>();
        particleSimulationScene.Name = Seed.ToString();
        AddChild(particleSimulationScene);
        particleSimulationScene.Initialize(nParticles);
        GetNode<Control>("MainMenu").Hide();
    }

    public void ExitToMenu()
    {
        GetNode(Seed.ToString()).QueueFree();
        GetNode<Control>("MainMenu").Show();
        GetNode<MainMenu>("MainMenu").RefreshSeedText();
    }

    public void RestartSimulation()
    {
        GetNode<ParticleSimulationScene>(Seed.ToString()).Hide();
        GetNode(Seed.ToString()).QueueFree();
        Seed = (int) GD.Randi();
        StartSimulation(_nParticles);
    }
    
}