diff --git a/src/bin/flat.rs b/src/bin/flat.rs
index f80add0..a13b80f 100644
--- a/src/bin/flat.rs
+++ b/src/bin/flat.rs
@@ -25,7 +25,8 @@ pub fn main() {
 		let canvas = create_drawing_window("Refraction");
 		canvas.draw(|gc| {
 			gc.canvas_height(1000.0);
-			space.render(gc);
+			space.draw_background(gc);
+			space.draw_rays(gc, &space);
 
 			let space = Rc::new(space);
 			let parts: Vec<Box<dyn SpacePart>> = vec![
@@ -33,14 +34,16 @@ pub fn main() {
 				Box::new(Wall { space: space.clone() }),
 				Box::new(Inside { space: space.clone() }),
 			];
-
-			parts.draw_fan(gc, vec2(-500.0, 0.0), vec2(1.0, 0.0), 1.0);
-			//	parts.draw_fan(gc, vec2(-20.0, -500.0), vec2(0.1, 0.9), 1.0);
-			//parts.draw_ray(gc, vec2(-20.0, -500.0), vec2(0.1, 0.9));
+			space.draw_rays(gc, parts.as_slice());
 		});
 	});
 }
 
+trait Interesting {
+	fn draw_background(&self, gc: &mut Vec<Draw>);
+	fn draw_rays(&self, gc: &mut Vec<Draw>, tracer: &(impl Rayable + ?Sized));
+}
+
 trait SpacePart: boundary::Boundary + Metric + SpaceVisual {}
 
 impl<T: boundary::Boundary + Metric + SpaceVisual> SpacePart for T {}
@@ -143,12 +146,8 @@ impl<T: Metric> Rayable for T {
 	}
 }
 
-trait Renderable {
-	fn render(&self, gc: &mut Vec<Draw>);
-}
-
-impl Renderable for Coil {
-	fn render(&self, gc: &mut Vec<Draw>) {
+impl Interesting for Coil {
+	fn draw_background(&self, gc: &mut Vec<Draw>) {
 		gc.new_path();
 		gc.circle(0.0, 0.0, self.r + self.w + self.m);
 		gc.circle(0.0, 0.0, self.r + self.w);
@@ -157,29 +156,35 @@ impl Renderable for Coil {
 		gc.winding_rule(WindingRule::EvenOdd);
 		gc.fill_color(Color::Rgba(0.8, 0.8, 0.8, 1.0));
 		gc.fill();
+	}
+
+	fn draw_rays(&self, gc: &mut Vec<Draw>, tracer: &(impl Rayable + ?Sized)) {
 		gc.line_width(0.5);
 		gc.stroke_color(Color::Rgba(1.0, 0.5, 0.0, 1.0));
-		self.draw_fan(gc, vec2(-500.0, 0.0), vec2(1.0, 0.0), 1.0);
+		tracer.draw_fan(gc, vec2(-500.0, 0.0), vec2(1.0, 0.0), 1.0);
 		gc.stroke_color(Color::Rgba(0.0, 0.5, 1.0, 1.0));
-		self.draw_fan(gc, vec2(0.0, self.r), vec2(1.0, 0.0), 1.0);
+		tracer.draw_fan(gc, vec2(0.0, self.r), vec2(1.0, 0.0), 1.0);
 	}
 }
 
-impl Renderable for Rect {
-	fn render(&self, gc: &mut Vec<Draw>) {
+impl Interesting for Rect {
+	fn draw_background(&self, gc: &mut Vec<Draw>) {
 		gc.new_path();
 		gc.rect(-self.outer_radius, -self.external_halflength, self.outer_radius, self.external_halflength);
 		gc.rect(-self.inner_radius, -self.external_halflength, self.inner_radius, self.external_halflength);
 		gc.winding_rule(WindingRule::EvenOdd);
 		gc.fill_color(Color::Rgba(0.8, 0.8, 0.8, 1.0));
 		gc.fill();
+	}
+
+	fn draw_rays(&self, gc: &mut Vec<Draw>, tracer: &(impl Rayable + ?Sized)) {
 		gc.line_width(0.5);
 		gc.stroke_color(Color::Rgba(1.0, 0.5, 0.0, 1.0));
-		self.draw_fan(gc, vec2(-500.0, 0.0), vec2(1.0, 0.0), 1.0);
+		tracer.draw_fan(gc, vec2(-500.0, 0.0), vec2(1.0, 0.0), 1.0);
 		gc.stroke_color(Color::Rgba(0.0, 0.5, 1.0, 1.0));
-		// self.draw_fan(gc, vec2(0.0, -0.5 * self.external_halflength), vec2(1.0, 1.0), 1.0);
+		tracer.draw_fan(gc, vec2(0.0, -0.5 * self.external_halflength), vec2(1.0, 1.0), 1.0);
 		gc.stroke_color(Color::Rgba(0.2, 0.7, 0.0, 1.0));
-		// self.draw_fan(gc, vec2(-0.5 * self.inner_radius, -1.2 * self.external_halflength), vec2(0.0, 1.0), 1.0);
+		tracer.draw_fan(gc, vec2(-0.5 * self.inner_radius, -1.2 * self.external_halflength), vec2(0.0, 1.0), 1.0);
 	}
 }