added ParticleType

ParticleType.cs

@@ -0,0 +1,38 @@
+using System.Collections.Generic;
+using Godot;
+
+public struct ParticleRelationshipProps
+{
+    public ParticleRelationshipProps(float minRadius, float maxRadius, float force)
+    {
+        MinRadius = minRadius;
+        MaxRadius = maxRadius;
+        Force = force;
+    }
+
+    public float MinRadius { get; }
+    public float MaxRadius { get; }
+    public float Force { get; }
+}
+
+public class ParticleType
+{
+    private float _hue;
+
+    private readonly Dictionary<ParticleType, ParticleRelationshipProps> _particleRelationships =
+        new Dictionary<ParticleType, ParticleRelationshipProps>();
+
+    public float Hue
+    {
+        get => _hue;
+        set => _hue = Mathf.Clamp(value, 0, 1);
+    }
+
+    public void AddRelationship(ParticleType type, float minRadius, float maxRadius, float force)
+    {
+        if (_particleRelationships.ContainsKey(type))
+            return;
+        var props = new ParticleRelationshipProps(minRadius, maxRadius, force);
+        _particleRelationships[type] = props;
+    }
+}