diff --git a/rtchallenge/examples/balls.rs b/rtchallenge/examples/balls.rs
new file mode 100644
index 0000000..0111172
--- /dev/null
+++ b/rtchallenge/examples/balls.rs
@@ -0,0 +1,92 @@
+use std::time::Instant;
+
+use anyhow::Result;
+use structopt::StructOpt;
+
+use rtchallenge::{
+    camera::{Camera, RenderStrategy},
+    float::consts::PI,
+    lights::PointLightBuilder,
+    materials::MaterialBuilder,
+    matrices::Matrix4x4,
+    shapes::{Geometry, ShapeBuilder},
+    transformations::view_transform,
+    tuples::Tuple,
+    world::WorldBuilder,
+    Float, WHITE,
+};
+
+/// End of chapter 9 challenge.
+#[derive(StructOpt, Debug)]
+#[structopt(name = "eoc9")]
+struct Opt {
+    #[structopt(long, default_value = "rayon")]
+    render_strategy: RenderStrategy,
+    /// Number of samples per pixel.  0 renders from the center of the pixel, 1 or more samples N
+    /// times randomly across the pixel.
+    #[structopt(short, long, default_value = "0")]
+    samples: usize,
+}
+
+fn main() -> Result<()> {
+    let start = Instant::now();
+    let opt = Opt::from_args();
+    let width = 2560;
+    let height = 1440;
+
+    let light1 = PointLightBuilder::default()
+        .position(Tuple::point(-5., 5., -5.))
+        .intensity(WHITE)
+        .build()?;
+    let light2 = PointLightBuilder::default()
+        .position(Tuple::point(5., 5., -5.))
+        .intensity([0.2, 0.2, 0.6])
+        .build()?;
+    let light3 = PointLightBuilder::default()
+        .position(Tuple::point(0., 2., -5.))
+        .intensity([0.2, 0.2, 0.1])
+        .build()?;
+
+    let from = Tuple::point(0., 1.5, -5.);
+    let to = Tuple::point(0., 1., 0.);
+    let up = Tuple::point(0., 1., 0.);
+    let mut camera = Camera::new(width, height, PI / 4.);
+    camera.set_transform(view_transform(from, to, up));
+    camera.render_strategy = opt.render_strategy;
+    camera.samples_per_pixel = opt.samples;
+
+    let floor = ShapeBuilder::default()
+        .geometry(Geometry::Plane)
+        .material(
+            MaterialBuilder::default()
+                .color([1., 0.2, 0.2])
+                .specular(0.)
+                .build()?,
+        )
+        .build()?;
+
+    const BALL_SIZE: Float = 0.2;
+    let middle = ShapeBuilder::default()
+        .transform(Matrix4x4::scaling(BALL_SIZE, BALL_SIZE, BALL_SIZE))
+        .material(
+            MaterialBuilder::default()
+                .color([0.1, 1., 0.5])
+                .diffuse(0.7)
+                .specular(0.3)
+                .build()?,
+        )
+        .build()?;
+
+    let world = WorldBuilder::default()
+        .lights(vec![light1, light2, light3])
+        .objects(vec![floor, middle])
+        .build()?;
+
+    let image = camera.render(&world);
+
+    let path = "/tmp/balls.png";
+    println!("saving output to {}", path);
+    image.write_to_file(path)?;
+    println!("Render time {:.3} seconds", start.elapsed().as_secs_f32());
+    Ok(())
+}