diff --git a/main.go b/main.go
index 05266ea..dd2ea34 100644
--- a/main.go
+++ b/main.go
@@ -61,21 +61,21 @@ func main() {
 				field: imageField,
 			},
 		}
+	sierpinskiLayer := &SierpinskiArrow { dirty: true }
 
 	sketch := NewSketch(sourceWidth, sourceHeight)
 
-	sierpinskiLayer := &SierpinskiArrow { dirty: true }
 
 	sketch.AddColorLayer("background-magenta", rl.Magenta)
-	//sketch.AddColorLayer("background-black", rl.Black)
+	sketch.AddColorLayer("background-black", rl.Black)
 	sketch.AddLayer("field", &FieldLayer{field: field, loColor: rl.NewColor(0, 0, 0, 0), hiColor: rl.Yellow, dirty: true})
 	contourLayer := NewContourLayer(&sketch, rng, field)
 	sketch.AddLayer("contours", contourLayer)
 	sketch.AddLayer("sierpinski-arrowhead", sierpinskiLayer)
-	//aurora := NewImageLayer("/home/d/Dropbox/photos/Events/2025/Aurora/Photo Nov 11 2025, 9 52 03 PM.jpg")
-	//sketch.AddLayer("aurora", aurora)
-	cave := NewImageLayer("/home/d/Dropbox/photos/Events/2025/ Chelsea and James visit Lindell/Photo Nov 29 2025, 5 26 40 PM (29).jpg")
-	sketch.AddLayer("cave", cave)
+//	aurora := NewImageLayer("/home/d/Dropbox/photos/Events/2025/Aurora/Photo Nov 11 2025, 9 52 03 PM.jpg")
+//	sketch.AddLayer("aurora", aurora)
+//	cave := NewImageLayer("/home/d/Dropbox/photos/Events/2025/ Chelsea and James visit Lindell/Photo Nov 29 2025, 5 26 40 PM (29).jpg")
+//	sketch.AddLayer("cave", cave)
 
 	ports := MakePorts()
 	ports["sierpinskiArrowAngle"] =
@@ -235,6 +235,8 @@ func (fl *FieldLayer) Update(ctx *RenderCtx) {
 }
 
 func (fl *FieldLayer) Draw(ctx *RenderCtx) {
+	rl.ClearBackground(rl.Blank)
+	rl.BeginBlendMode(rl.BlendAlphaPremultiply)
 	for x := range ctx.SourceWidth {
 		for y := range ctx.SourceHeight {
 			v := fl.field.Get(float32(x), float32(y))
@@ -242,6 +244,7 @@ func (fl *FieldLayer) Draw(ctx *RenderCtx) {
 			rl.DrawPixel(x, y, clr)
 		}
 	}
+	rl.EndBlendMode()
 	fl.dirty = false
 }
 
diff --git a/sketch.go b/sketch.go
index b76e03d..6b36176 100644
--- a/sketch.go
+++ b/sketch.go
@@ -127,8 +127,40 @@ func (s *Sketch) Draw(ctx *RenderCtx) {
 	}
 
 	viewport := s.CalcViewport(ctx)
+	outputRect := s.calcOutputRectKeepingAspectRatio(ctx)
+
+	x := float32(0)
+	y := float32(0)
+	w := outputRect.Width
+	h := outputRect.Height
+	rl.PushMatrix()
+	rl.Translatef(outputRect.X, outputRect.Y, 0)
+	rl.BeginScissorMode(int32(outputRect.X), int32(outputRect.Y), int32(outputRect.Width), int32(outputRect.Height))
+	checkSize := float32(25.0)
+	grey := rl.NewColor(220, 220, 220, 255)
+	cellX := 0
+	cellY := 0
+	for y < h {
+		x = 0
+		cellX = 0
+		for x < w {
+			c := rl.White
+			if ((cellX + cellY) & 1) == 1 {
+				c = grey
+			}
+			rl.DrawRectangle(int32(x), int32(y), int32(checkSize), int32(checkSize), c)
+			x += checkSize
+			cellX++
+		}
+		y += checkSize
+		cellY++
+	}
+	rl.EndScissorMode()
+	rl.PopMatrix()
+
 
 	rl.BeginBlendMode(rl.BlendAlphaPremultiply)
+	//rl.BeginBlendMode(rl.BlendAlpha)
 	rl.BeginTextureMode(s.composite)
 	rl.ClearBackground(rl.Blank)
 	//rl.ClearBackground(rl.Black)
@@ -147,6 +179,9 @@ func (s *Sketch) Draw(ctx *RenderCtx) {
 			if config.bVisible {
 				b = config.b
 			}
+			r = uint8(float32(r) * (float32(config.a) / 255.0))
+			g = uint8(float32(g) * (float32(config.a) / 255.0))
+			b = uint8(float32(b) * (float32(config.a) / 255.0))
 			tint := rl.NewColor(r, g, b, config.a)
 			rl.DrawTexturePro(instance.texture.Texture, src, dst, rl.Vector2{}, 0, tint)
 		}
@@ -157,7 +192,6 @@ func (s *Sketch) Draw(ctx *RenderCtx) {
 	rl.GenTextureMipmaps(&s.composite.Texture)
 	rl.SetTextureFilter(s.composite.Texture, rl.FilterTrilinear)
 
-	outputRect := s.calcOutputRectKeepingAspectRatio(ctx)
 	rl.DrawTexturePro(s.composite.Texture, viewport, outputRect, rl.Vector2{}, 0, rl.White)
 
 	outlineRect := outputRect.ToInt32()