fix: color lerping not working properly

Engine.Core/Primitives/ColorRGB.cs

@@ -95,7 +95,11 @@ public readonly struct ColorRGB(byte r, byte g, byte b) : IEquatable<ColorRGB>
         int greenDiff = to.G - from.G;
         int blueDiff = to.B - from.B;
 
-        return from + new ColorRGB((byte)(redDiff * t), (byte)(greenDiff * t), (byte)(blueDiff * t));
+        return new(
+            (byte)(from.R + redDiff * t),
+            (byte)(from.G + greenDiff * t),
+            (byte)(from.B + blueDiff * t)
+        );
     }
 
     /// <summary>

Engine.Core/Primitives/ColorRGBA.cs

@@ -1,4 +1,5 @@
 using System;
+using Engine.Core.Debug;
 
 namespace Engine.Core;
 
@@ -125,7 +126,12 @@ public readonly struct ColorRGBA(byte r, byte g, byte b, byte a = 255) : IEquata
         int blueDiff = to.B - from.B;
         int alphaDiff = to.A - from.A;
 
-        return from + new ColorRGBA((byte)(redDiff * t), (byte)(greenDiff * t), (byte)(blueDiff * t), (byte)(alphaDiff * t));
+        return new(
+            (byte)(from.R + redDiff * t),
+            (byte)(from.G + greenDiff * t),
+            (byte)(from.B + blueDiff * t),
+            (byte)(from.A + alphaDiff * t)
+        );
     }
 
     /// <summary>

Engine.Integration/Engine.Integration.MonoGame/MonoGameTriangleBatch.cs

@@ -39,7 +39,7 @@ public class MonoGameTriangleBatch : Behaviour, ITriangleBatch, IFirstFrameUpdat
         Vector2 A = triangle.A.ToVector2();
         Vector2 B = triangle.B.ToVector2();
         Vector2 C = triangle.C.ToVector2();
-        Color color = colorRGBA.ToColor();
+        Color color = colorRGBA.ToPreMultipliedColor();
 
         vertices[verticesIndex++] = new(new(A.X, A.Y, 0f), color);
         vertices[verticesIndex++] = new(new(B.X, B.Y, 0f), color);
@@ -60,6 +60,8 @@ public class MonoGameTriangleBatch : Behaviour, ITriangleBatch, IFirstFrameUpdat
             return;
 
         graphicsDevice.RasterizerState = rasterizerState;
+        graphicsDevice.BlendState = BlendState.AlphaBlend;
+
         basicEffect.Projection = projection;
         basicEffect.View = view;
         vertexBuffer.SetData(vertices);
@@ -67,8 +69,10 @@ public class MonoGameTriangleBatch : Behaviour, ITriangleBatch, IFirstFrameUpdat
         graphicsDevice.SetVertexBuffer(vertexBuffer);
 
         foreach (EffectPass pass in basicEffect.CurrentTechnique.Passes)
+        {
             pass.Apply();
-        graphicsDevice.DrawPrimitives(PrimitiveType.TriangleList, 0, verticesIndex / 3);
+            graphicsDevice.DrawPrimitives(PrimitiveType.TriangleList, 0, verticesIndex / 3);
+        }
 
         verticesIndex = 0;
     }