particles/Main.cs

using Godot;
using System;
using Particles.ParticleSimulation;

public class Main : Node
{

    public int Seed;
    public float Zoom;
    
    private int _nParticles;

    public override void _Ready()
    {
        OS.MinWindowSize = new Vector2(1024, 600);
    }

    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(Seed, nParticles, Zoom);
        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 = Mathf.Abs((int)GD.Randi());
        StartSimulation(_nParticles);
    }
    
}