diff --git a/rtchallenge/examples/eoc5.rs b/rtchallenge/examples/eoc5.rs
index c30baf5..ece1ffa 100644
--- a/rtchallenge/examples/eoc5.rs
+++ b/rtchallenge/examples/eoc5.rs
@@ -4,7 +4,7 @@ use rtchallenge::{
     canvas::Canvas,
     matrices::Matrix4x4,
     rays::Ray,
-    spheres::{intersect, Sphere},
+    shapes::{intersect, Shape},
     tuples::{Color, Tuple},
     Float,
 };
@@ -20,7 +20,7 @@ fn main() -> Result<()> {
     let pixel_size = wall_size / w as Float;
     let half = wall_size / 2.;
     let color = Color::new(1., 0., 0.);
-    let mut shape = Sphere::default();
+    let mut shape = Shape::sphere();
     shape.set_transform(
         Matrix4x4::shearing(1., 0., 0., 0., 0., 0.) * Matrix4x4::scaling(0.5, 1., 1.0),
     );
diff --git a/rtchallenge/examples/eoc6.rs b/rtchallenge/examples/eoc6.rs
index c597296..41cbba6 100644
--- a/rtchallenge/examples/eoc6.rs
+++ b/rtchallenge/examples/eoc6.rs
@@ -5,7 +5,7 @@ use rtchallenge::{
     lights::PointLight,
     materials::{lighting, Material},
     rays::Ray,
-    spheres::{intersect, Sphere},
+    shapes::{intersect, Shape},
     tuples::{Color, Tuple},
     Float, WHITE,
 };
@@ -20,7 +20,7 @@ fn main() -> Result<()> {
     let wall_size = 7.;
     let pixel_size = wall_size / w as Float;
     let half = wall_size / 2.;
-    let mut shape = Sphere::default();
+    let mut shape = Shape::sphere();
     shape.material = Material {
         color: Color::new(1., 0.2, 1.),
         specular: 0.5,
diff --git a/rtchallenge/examples/eoc7.rs b/rtchallenge/examples/eoc7.rs
index 146d84c..54118d9 100644
--- a/rtchallenge/examples/eoc7.rs
+++ b/rtchallenge/examples/eoc7.rs
@@ -9,7 +9,7 @@ use rtchallenge::{
     lights::PointLight,
     materials::Material,
     matrices::Matrix4x4,
-    spheres::Sphere,
+    shapes::Shape,
     transformations::view_transform,
     tuples::{Color, Tuple},
     world::World,
@@ -39,7 +39,7 @@ fn main() -> Result<()> {
     camera.set_transform(view_transform(from, to, up));
     camera.render_strategy = opt.render_strategy;
 
-    let mut floor = Sphere::default();
+    let mut floor = Shape::sphere();
     floor.set_transform(Matrix4x4::scaling(10., 0.01, 10.));
     floor.material = Material {
         color: Color::new(1., 0.9, 0.9),
@@ -47,7 +47,7 @@ fn main() -> Result<()> {
         ..Material::default()
     };
 
-    let mut left_wall = Sphere::default();
+    let mut left_wall = Shape::sphere();
     left_wall.set_transform(
         Matrix4x4::translation(0., 0., 5.)
             * Matrix4x4::rotation_y(-PI / 4.)
@@ -56,7 +56,7 @@ fn main() -> Result<()> {
     );
     left_wall.material = floor.material.clone();
 
-    let mut right_wall = Sphere::default();
+    let mut right_wall = Shape::sphere();
     right_wall.set_transform(
         Matrix4x4::translation(0., 0., 5.)
             * Matrix4x4::rotation_y(PI / 4.)
@@ -65,7 +65,7 @@ fn main() -> Result<()> {
     );
     right_wall.material = floor.material.clone();
 
-    let mut middle = Sphere::default();
+    let mut middle = Shape::sphere();
     middle.set_transform(Matrix4x4::translation(-0.5, 1., 0.5));
     middle.material = Material {
         color: Color::new(0.1, 1., 0.5),
@@ -74,7 +74,7 @@ fn main() -> Result<()> {
         ..Material::default()
     };
 
-    let mut right = Sphere::default();
+    let mut right = Shape::sphere();
     right.set_transform(Matrix4x4::translation(1.5, 0.5, -0.5) * Matrix4x4::scaling(0.5, 0.5, 0.5));
     right.material = Material {
         color: Color::new(0.5, 1., 0.1),
@@ -83,7 +83,7 @@ fn main() -> Result<()> {
         ..Material::default()
     };
 
-    let mut left = Sphere::default();
+    let mut left = Shape::sphere();
     left.set_transform(
         Matrix4x4::translation(-1.5, 0.33, -0.75) * Matrix4x4::scaling(0.33, 0.33, 0.33),
     );
diff --git a/rtchallenge/examples/eoc8.rs b/rtchallenge/examples/eoc8.rs
index ae027fd..4fde11d 100644
--- a/rtchallenge/examples/eoc8.rs
+++ b/rtchallenge/examples/eoc8.rs
@@ -9,7 +9,7 @@ use rtchallenge::{
     lights::PointLight,
     materials::Material,
     matrices::Matrix4x4,
-    spheres::Sphere,
+    shapes::Shape,
     transformations::view_transform,
     tuples::{Color, Tuple},
     world::World,
@@ -51,7 +51,7 @@ fn main() -> Result<()> {
     camera.render_strategy = opt.render_strategy;
     camera.samples_per_pixel = opt.samples;
 
-    let mut floor = Sphere::default();
+    let mut floor = Shape::sphere();
     floor.set_transform(Matrix4x4::scaling(10., 0.01, 10.));
     floor.material = Material {
         color: Color::new(1., 0.9, 0.9),
@@ -59,7 +59,7 @@ fn main() -> Result<()> {
         ..Material::default()
     };
 
-    let mut left_wall = Sphere::default();
+    let mut left_wall = Shape::sphere();
     left_wall.set_transform(
         Matrix4x4::translation(0., 0., 5.)
             * Matrix4x4::rotation_y(-PI / 4.)
@@ -68,7 +68,7 @@ fn main() -> Result<()> {
     );
     left_wall.material = floor.material.clone();
 
-    let mut right_wall = Sphere::default();
+    let mut right_wall = Shape::sphere();
     right_wall.set_transform(
         Matrix4x4::translation(0., 0., 5.)
             * Matrix4x4::rotation_y(PI / 4.)
@@ -77,7 +77,7 @@ fn main() -> Result<()> {
     );
     right_wall.material = floor.material.clone();
 
-    let mut middle = Sphere::default();
+    let mut middle = Shape::sphere();
     middle.set_transform(Matrix4x4::translation(-0.5, 1., 0.5));
     middle.material = Material {
         color: Color::new(0.1, 1., 0.5),
@@ -86,7 +86,7 @@ fn main() -> Result<()> {
         ..Material::default()
     };
 
-    let mut right = Sphere::default();
+    let mut right = Shape::sphere();
     right.set_transform(Matrix4x4::translation(1.5, 0.5, -0.5) * Matrix4x4::scaling(0.5, 0.5, 0.5));
     right.material = Material {
         color: Color::new(1., 1., 1.),
@@ -95,7 +95,7 @@ fn main() -> Result<()> {
         ..Material::default()
     };
 
-    let mut left = Sphere::default();
+    let mut left = Shape::sphere();
     left.set_transform(
         Matrix4x4::translation(-1.5, 0.33, -0.75) * Matrix4x4::scaling(0.33, 0.33, 0.33),
     );
diff --git a/rtchallenge/src/intersections.rs b/rtchallenge/src/intersections.rs
index c4bd263..2802eb4 100644
--- a/rtchallenge/src/intersections.rs
+++ b/rtchallenge/src/intersections.rs
@@ -2,7 +2,7 @@ use std::ops::Index;
 
 use crate::{
     rays::Ray,
-    spheres::Sphere,
+    shapes::Shape,
     tuples::{dot, Tuple},
     Float, EPSILON,
 };
@@ -10,7 +10,7 @@ use crate::{
 #[derive(Debug, Clone, PartialEq)]
 pub struct Intersection<'i> {
     pub t: Float,
-    pub object: &'i Sphere,
+    pub object: &'i Shape,
 }
 
 impl<'i> Intersection<'i> {
@@ -18,15 +18,15 @@ impl<'i> Intersection<'i> {
     ///
     /// # Examples
     /// ```
-    /// use rtchallenge::{intersections::Intersection, spheres::Sphere};
+    /// use rtchallenge::{intersections::Intersection, shapes::Shape};
     ///
     /// // An intersection ecapsulates t and object.
-    /// let s = Sphere::default();
+    /// let s = Shape::sphere();
     /// let i = Intersection::new(3.5, &s);
     /// assert_eq!(i.t, 3.5);
     /// assert_eq!(i.object, &s);
     /// ```
-    pub fn new(t: Float, object: &Sphere) -> Intersection {
+    pub fn new(t: Float, object: &Shape) -> Intersection {
         Intersection { t, object }
     }
 }
@@ -38,11 +38,11 @@ impl<'i> Intersection<'i> {
 /// use rtchallenge::{
 ///     intersections::{Intersection, Intersections},
 ///     rays::Ray,
-///     spheres::{intersect, Sphere},
+///     shapes::{intersect, Shape},
 ///     tuples::Tuple,
 /// };
 ///
-/// let s = Sphere::default();
+/// let s = Shape::sphere();
 /// let i1 = Intersection::new(1., &s);
 /// let i2 = Intersection::new(2., &s);
 /// let xs = Intersections::new(vec![i1, i2]);
@@ -73,12 +73,12 @@ impl<'i> Intersections<'i> {
     /// use rtchallenge::{
     ///     intersections::{Intersection, Intersections},
     ///     rays::Ray,
-    ///     spheres::{intersect, Sphere},
+    ///     shapes::{intersect, Shape},
     ///     tuples::Tuple,
     /// };
     ///
     /// // The hit, when all intersections have positive t.
-    /// let s = Sphere::default();
+    /// let s = Shape::sphere();
     /// let i1 = Intersection::new(1., &s);
     /// let i2 = Intersection::new(2., &s);
     /// let xs = Intersections::new(vec![i2, i1.clone()]);
@@ -86,7 +86,7 @@ impl<'i> Intersections<'i> {
     /// assert_eq!(i, Some(&i1));
     ///
     /// // The hit, when some intersections have negative t.
-    /// let s = Sphere::default();
+    /// let s = Shape::sphere();
     /// let i1 = Intersection::new(-1., &s);
     /// let i2 = Intersection::new(1., &s);
     /// let xs = Intersections::new(vec![i2.clone(), i1]);
@@ -94,7 +94,7 @@ impl<'i> Intersections<'i> {
     /// assert_eq!(i, Some(&i2));
     ///
     /// // The hit, when all intersections have negative t.
-    /// let s = Sphere::default();
+    /// let s = Shape::sphere();
     /// let i1 = Intersection::new(-2., &s);
     /// let i2 = Intersection::new(-1., &s);
     /// let xs = Intersections::new(vec![i2, i1]);
@@ -102,7 +102,7 @@ impl<'i> Intersections<'i> {
     /// assert_eq!(i, None);
     ///
     /// // The hit is always the lowest nonnegative intersection.
-    /// let s = Sphere::default();
+    /// let s = Shape::sphere();
     /// let i1 = Intersection::new(5., &s);
     /// let i2 = Intersection::new(7., &s);
     /// let i3 = Intersection::new(-3., &s);
@@ -138,7 +138,7 @@ impl<'i> Index<usize> for Intersections<'i> {
 #[derive(Debug)]
 pub struct PrecomputedData<'i> {
     pub t: Float,
-    pub object: &'i Sphere,
+    pub object: &'i Shape,
     pub point: Tuple,
     pub over_point: Tuple,
     pub eyev: Tuple,
@@ -154,14 +154,14 @@ pub struct PrecomputedData<'i> {
 ///     intersections::{prepare_computations, Intersection, Intersections},
 ///     rays::Ray,
 ///     matrices::Matrix4x4,
-///     spheres::{intersect, Sphere},
+///     shapes::{intersect, Shape},
 ///     tuples::Tuple,
 ///     EPSILON
 /// };
 ///
 /// // Precomputing the state of an intersection.
 /// let r = Ray::new(Tuple::point(0., 0., -5.), Tuple::vector(0., 0., 1.));
-/// let shape = Sphere::default();
+/// let shape = Shape::sphere();
 /// let i = Intersection::new(4., &shape);
 /// let comps = prepare_computations(&i, &r);
 /// assert_eq!(comps.t, i.t);
@@ -172,14 +172,14 @@ pub struct PrecomputedData<'i> {
 ///
 /// // The hit, when an intersection occurs on the outside.
 /// let r = Ray::new(Tuple::point(0., 0., -5.), Tuple::vector(0., 0., 1.));
-/// let shape = Sphere::default();
+/// let shape = Shape::sphere();
 /// let i = Intersection::new(4., &shape);
 /// let comps = prepare_computations(&i, &r);
 /// assert_eq!(comps.inside, false);
 ///
 /// // The hit, when an intersection occurs on the inside.
 /// let r = Ray::new(Tuple::point(0., 0., 0.), Tuple::vector(0., 0., 1.));
-/// let shape = Sphere::default();
+/// let shape = Shape::sphere();
 /// let i = Intersection::new(1., &shape);
 /// let comps = prepare_computations(&i, &r);
 /// assert_eq!(comps.point, Tuple::point(0., 0., 1.));
@@ -190,7 +190,7 @@ pub struct PrecomputedData<'i> {
 ///
 /// // The hit should offset the point.
 /// let r = Ray::new(Tuple::point(0., 0., -5.), Tuple::vector(0., 0., 1.));
-/// let mut shape = Sphere::default();
+/// let mut shape = Shape::sphere();
 /// shape .set_transform(Matrix4x4::translation(0.,0.,1.));
 /// let i = Intersection::new(5., &shape);
 /// let comps = prepare_computations(&i, &r);
diff --git a/rtchallenge/src/lib.rs b/rtchallenge/src/lib.rs
index 8b7839f..d02e1b0 100644
--- a/rtchallenge/src/lib.rs
+++ b/rtchallenge/src/lib.rs
@@ -5,7 +5,7 @@ pub mod lights;
 pub mod materials;
 pub mod matrices;
 pub mod rays;
-pub mod spheres;
+pub mod shapes;
 pub mod transformations;
 pub mod tuples;
 pub mod world;
diff --git a/rtchallenge/src/spheres.rs b/rtchallenge/src/shapes.rs
similarity index 69%
rename from rtchallenge/src/spheres.rs
rename to rtchallenge/src/shapes.rs
index d420974..9116666 100644
--- a/rtchallenge/src/spheres.rs
+++ b/rtchallenge/src/shapes.rs
@@ -7,71 +7,80 @@ use crate::{
 };
 
 #[derive(Debug, PartialEq, Clone)]
-/// Sphere represents the unit-sphere (radius of unit 1.) at the origin 0., 0., 0.
-pub struct Sphere {
+enum Geometry {
+    /// Sphere represents the unit-sphere (radius of unit 1.) at the origin 0., 0., 0.
+    Sphere,
+}
+
+/// Shape represents visible objects.  A signal instance of Shape can generically represent one of
+/// many different shapes based on the value of it's geometry field.  Users chose the shape by
+/// calling the appropriate constructor, i.e. [Shape::sphere].
+#[derive(Debug, PartialEq, Clone)]
+pub struct Shape {
     transform: Matrix4x4,
     inverse_transform: Matrix4x4,
     pub material: Material,
+    geometry: Geometry,
 }
 
-impl Default for Sphere {
+impl Shape {
     /// # Examples
     /// ```
-    /// use rtchallenge::{materials::Material, matrices::Matrix4x4, spheres::Sphere};
+    /// use rtchallenge::{materials::Material, matrices::Matrix4x4, shapes::Shape};
     ///
     /// // A sphere's default transform is the identity matrix.
-    /// let s = Sphere::default();
+    /// let s = Shape::sphere();
     /// assert_eq!(s.transform(), Matrix4x4::identity());
     ///
     /// // It can be changed by directly setting the transform member.
-    /// let mut s = Sphere::default();
+    /// let mut s = Shape::sphere();
     /// let t = Matrix4x4::translation(2., 3., 4.);
-    /// s.set_transform ( t.clone());
+    /// s.set_transform(t.clone());
     /// assert_eq!(s.transform(), t);
     ///
     /// // Default Sphere has the default material.
     /// assert_eq!(s.material, Material::default());
     /// // It can be overridden.
-    /// let mut s = Sphere::default();
+    /// let mut s = Shape::sphere();
     /// let mut m = Material::default();
     /// m.ambient = 1.;
     /// s.material = m.clone();
     /// assert_eq!(s.material, m);
-
     /// ```
-    fn default() -> Sphere {
-        Sphere {
+    pub fn sphere() -> Shape {
+        Shape {
             transform: Matrix4x4::identity(),
             inverse_transform: Matrix4x4::identity(),
             material: Material::default(),
+            geometry: Geometry::Sphere,
         }
     }
-}
-
-impl Sphere {
     /// Find the normal at the point on the sphere.
     ///
     /// # Examples
     /// ```
-    /// use rtchallenge::{matrices::Matrix4x4, spheres::Sphere, tuples::Tuple,Float};
+    /// use rtchallenge::{
+    ///     float::consts::PI, materials::Material, matrices::Matrix4x4, shapes::Shape, tuples::Tuple,
+    ///     Float,
+    /// };
     ///
     /// // Normal on X-axis
-    /// let s = Sphere::default();
+    /// let s = Shape::sphere();
     /// let n = s.normal_at(Tuple::point(1., 0., 0.));
     /// assert_eq!(n, Tuple::vector(1., 0., 0.));
     ///
     /// // Normal on Y-axis
-    /// let s = Sphere::default();
+    /// let s = Shape::sphere();
     /// let n = s.normal_at(Tuple::point(0., 1., 0.));
     /// assert_eq!(n, Tuple::vector(0., 1., 0.));
     ///
     /// // Normal on Z-axis
-    /// let s = Sphere::default();
+    /// let s = Shape::sphere();
     /// let n = s.normal_at(Tuple::point(0., 0., 1.));
     /// assert_eq!(n, Tuple::vector(0., 0., 1.));
     ///
     /// // Normal on a sphere at a nonaxial point.
-    /// let s = Sphere::default();
+    /// let s = Shape::sphere();
     /// let n = s.normal_at(Tuple::point(
     ///     (3. as Float).sqrt() / 3.,
     ///     (3. as Float).sqrt() / 3.,
@@ -79,10 +88,14 @@ impl Sphere {
     /// ));
     /// assert_eq!(
     ///     n,
-    ///     Tuple::vector((3. as Float).sqrt() / 3., (3. as Float).sqrt() / 3., (3. as Float).sqrt() / 3.,)
+    ///     Tuple::vector(
+    ///         (3. as Float).sqrt() / 3.,
+    ///         (3. as Float).sqrt() / 3.,
+    ///         (3. as Float).sqrt() / 3.,
+    ///     )
     /// );
     /// // Normals returned are normalized.
-    /// let s = Sphere::default();
+    /// let s = Shape::sphere();
     /// let n = s.normal_at(Tuple::point(
     ///     (3. as Float).sqrt() / 3.,
     ///     (3. as Float).sqrt() / 3.,
@@ -91,23 +104,27 @@ impl Sphere {
     /// assert_eq!(n, n.normalize());
     ///
     /// // Compute the normal on a translated sphere.
-    /// let mut s = Sphere::default();
-    /// s.set_transform ( Matrix4x4::translation(0., 1., 0.));
+    /// let mut s = Shape::sphere();
+    /// s.set_transform(Matrix4x4::translation(0., 1., 0.));
     /// let n = s.normal_at(Tuple::point(0., 1.70711, -0.70711));
     /// assert_eq!(n, Tuple::vector(0., 0.70711, -0.70711));
-
-    /// // Compute the normal on a transformed sphere.
-    /// use rtchallenge::float::consts::PI;
     ///
-    /// let mut s = Sphere::default();
-    /// s.set_transform ( Matrix4x4::scaling(1.,0.5,1.) * Matrix4x4::rotation_z(PI/5.));
-    /// let n = s.normal_at(Tuple::point(0., (2. as Float).sqrt()/2., -(2. as Float).sqrt()/2.));
+    /// // Compute the normal on a transformed sphere.
+    /// let mut s = Shape::sphere();
+    /// s.set_transform(Matrix4x4::scaling(1., 0.5, 1.) * Matrix4x4::rotation_z(PI / 5.));
+    /// let n = s.normal_at(Tuple::point(
+    ///     0.,
+    ///     (2. as Float).sqrt() / 2.,
+    ///     -(2. as Float).sqrt() / 2.,
+    /// ));
     /// assert_eq!(n, Tuple::vector(0., 0.97014, -0.24254));
     /// ```
     #[cfg(not(feature = "disable-inverse-cache"))]
     pub fn normal_at(&self, world_point: Tuple) -> Tuple {
         let object_point = self.inverse_transform * world_point;
-        let object_normal = object_point - Tuple::point(0., 0., 0.);
+        let object_normal = match self.geometry {
+            Geometry::Sphere => object_point - Tuple::point(0., 0., 0.),
+        };
         let mut world_normal = self.inverse_transform.transpose() * object_normal;
         world_normal.w = 0.;
         world_normal.normalize()
@@ -115,7 +132,9 @@ impl Sphere {
     #[cfg(feature = "disable-inverse-cache")]
     pub fn normal_at(&self, world_point: Tuple) -> Tuple {
         let object_point = self.transform.inverse() * world_point;
-        let object_normal = object_point - Tuple::point(0., 0., 0.);
+        let object_normal = match self.geometry {
+            Geometry::Sphere => object_point - Tuple::point(0., 0., 0.),
+        };
         let mut world_normal = self.transform.inverse().transpose() * object_normal;
         world_normal.w = 0.;
         world_normal.normalize()
@@ -124,6 +143,7 @@ impl Sphere {
     pub fn transform(&self) -> Matrix4x4 {
         self.transform
     }
+
     pub fn set_transform(&mut self, t: Matrix4x4) {
         self.transform = t;
         self.inverse_transform = t.inverse();
@@ -138,13 +158,13 @@ impl Sphere {
 ///     intersections::{Intersection, Intersections},
 ///     matrices::Matrix4x4,
 ///     rays::Ray,
-///     spheres::{intersect, Sphere},
+///     shapes::{intersect, Shape},
 ///     tuples::Tuple,
 /// };
 ///
 /// // A ray intersects a sphere in two points.
 /// let r = Ray::new(Tuple::point(0., 0., -5.), Tuple::vector(0., 0., 1.));
-/// let s = Sphere::default();
+/// let s = Shape::sphere();
 /// let xs = intersect(&s, &r);
 /// assert_eq!(
 ///     xs,
@@ -153,13 +173,13 @@ impl Sphere {
 ///
 /// // A ray intersects a sphere at a tangent.
 /// let r = Ray::new(Tuple::point(0., 2., -5.), Tuple::vector(0., 0., 1.));
-/// let s = Sphere::default();
+/// let s = Shape::sphere();
 /// let xs = intersect(&s, &r);
 /// assert_eq!(xs, Intersections::default());
 ///
 /// // A ray originates inside a sphere.
 /// let r = Ray::new(Tuple::point(0., 0., 0.), Tuple::vector(0., 0., 1.));
-/// let s = Sphere::default();
+/// let s = Shape::sphere();
 /// let xs = intersect(&s, &r);
 /// assert_eq!(
 ///     xs,
@@ -168,7 +188,7 @@ impl Sphere {
 ///
 /// // A sphere is behind a ray.
 /// let r = Ray::new(Tuple::point(0., 0., 5.), Tuple::vector(0., 0., 1.));
-/// let s = Sphere::default();
+/// let s = Shape::sphere();
 /// let xs = intersect(&s, &r);
 /// assert_eq!(
 ///     xs,
@@ -177,7 +197,7 @@ impl Sphere {
 ///
 /// // Intersect a scaled sphere with a ray.
 /// let r = Ray::new(Tuple::point(0., 0., -5.), Tuple::vector(0., 0., 1.));
-/// let mut s = Sphere::default();
+/// let mut s = Shape::sphere();
 /// s.set_transform(Matrix4x4::scaling(2., 2., 2.));
 /// let xs = intersect(&s, &r);
 /// assert_eq!(xs.len(), 2, "xs {:?}", xs);
@@ -186,17 +206,19 @@ impl Sphere {
 ///
 /// // Intersect a translated sphere with a ray.
 /// let r = Ray::new(Tuple::point(0., 0., -5.), Tuple::vector(0., 0., 1.));
-/// let mut s = Sphere::default();
+/// let mut s = Shape::sphere();
 /// s.set_transform(Matrix4x4::translation(5., 0., 0.));
 /// let xs = intersect(&s, &r);
 /// assert_eq!(xs.len(), 0);
 /// ```
-pub fn intersect<'s>(sphere: &'s Sphere, ray: &Ray) -> Intersections<'s> {
-    intersect_rtc(sphere, ray)
+pub fn intersect<'s>(shape: &'s Shape, ray: &Ray) -> Intersections<'s> {
+    match shape.geometry {
+        Geometry::Sphere => intersect_rtc(shape, ray),
+    }
 }
 
-fn intersect_rtc<'s>(sphere: &'s Sphere, ray: &Ray) -> Intersections<'s> {
-    let ray = ray.transform(sphere.inverse_transform);
+fn intersect_rtc<'s>(shape: &'s Shape, ray: &Ray) -> Intersections<'s> {
+    let ray = ray.transform(shape.inverse_transform);
     let sphere_to_ray = ray.origin - Tuple::point(0., 0., 0.);
     let a = dot(ray.direction, ray.direction);
     let b = 2. * dot(ray.direction, sphere_to_ray);
@@ -206,12 +228,12 @@ fn intersect_rtc<'s>(sphere: &'s Sphere, ray: &Ray) -> Intersections<'s> {
         return Intersections::default();
     }
     Intersections::new(vec![
-        Intersection::new((-b - discriminant.sqrt()) / (2. * a), &sphere),
-        Intersection::new((-b + discriminant.sqrt()) / (2. * a), &sphere),
+        Intersection::new((-b - discriminant.sqrt()) / (2. * a), &shape),
+        Intersection::new((-b + discriminant.sqrt()) / (2. * a), &shape),
     ])
 }
-fn intersect_rtiow<'s>(sphere: &'s Sphere, ray: &Ray) -> Intersections<'s> {
-    let ray = ray.transform(sphere.inverse_transform);
+fn intersect_rtiow<'s>(shape: &'s Shape, ray: &Ray) -> Intersections<'s> {
+    let ray = ray.transform(shape.inverse_transform);
     let oc = ray.origin - Tuple::point(0., 0., 0.);
     let a = dot(ray.direction, ray.direction);
     let b = dot(oc, ray.direction);
@@ -221,7 +243,7 @@ fn intersect_rtiow<'s>(sphere: &'s Sphere, ray: &Ray) -> Intersections<'s> {
         return Intersections::default();
     }
     Intersections::new(vec![
-        Intersection::new((-b - discriminant.sqrt()) / a, &sphere),
-        Intersection::new((-b + discriminant.sqrt()) / a, &sphere),
+        Intersection::new((-b - discriminant.sqrt()) / a, &shape),
+        Intersection::new((-b + discriminant.sqrt()) / a, &shape),
     ])
 }
diff --git a/rtchallenge/src/world.rs b/rtchallenge/src/world.rs
index d4f93c0..4fc9f53 100644
--- a/rtchallenge/src/world.rs
+++ b/rtchallenge/src/world.rs
@@ -4,7 +4,7 @@ use crate::{
     materials::{lighting, Material},
     matrices::Matrix4x4,
     rays::Ray,
-    spheres::{intersect, Sphere},
+    shapes::{intersect, Shape},
     tuples::{Color, Tuple},
     Float, BLACK, WHITE,
 };
@@ -23,7 +23,7 @@ use crate::{
 #[derive(Clone, Debug, Default)]
 pub struct World {
     pub lights: Vec<PointLight>,
-    pub objects: Vec<Sphere>,
+    pub objects: Vec<Shape>,
 }
 
 impl World {
@@ -39,14 +39,14 @@ impl World {
     /// ```
     pub fn test_world() -> World {
         let light = PointLight::new(Tuple::point(-10., 10., -10.), WHITE);
-        let mut s1 = Sphere::default();
+        let mut s1 = Shape::sphere();
         s1.material = Material {
             color: Color::new(0.8, 1., 0.6),
             diffuse: 0.7,
             specular: 0.2,
             ..Material::default()
         };
-        let mut s2 = Sphere::default();
+        let mut s2 = Shape::sphere();
         s2.set_transform(Matrix4x4::scaling(0.5, 0.5, 0.5));
         World {
             lights: vec![light],
@@ -92,7 +92,7 @@ impl World {
     ///     lights::PointLight,
     ///     matrices::Matrix4x4,
     ///     rays::Ray,
-    ///     spheres::Sphere,
+    ///     shapes::Shape,
     ///     tuples::{Color, Tuple},
     ///     world::World,
     ///     WHITE,
@@ -120,8 +120,8 @@ impl World {
     /// // Shading with an intersection in shadow.
     /// let mut w = World::default();
     /// w.lights = vec![PointLight::new(Tuple::point(0., 0., -10.), WHITE)];
-    /// let s1 = Sphere::default();
-    /// let mut s2 = Sphere::default();
+    /// let s1 = Shape::sphere();
+    /// let mut s2 = Shape::sphere();
     /// s2.set_transform(Matrix4x4::translation(0., 0., 10.));
     /// w.objects = vec![s1, s2.clone()];
     /// let r = Ray::new(Tuple::point(0., 0., 5.), Tuple::vector(0., 0., 1.));
@@ -155,6 +155,7 @@ impl World {
     ///     intersections::{prepare_computations, Intersection},
     ///     lights::PointLight,
     ///     rays::Ray,
+    ///     shapes::Shape,
     ///     tuples::{Color, Tuple},
     ///     world::World,
     ///     BLACK,
@@ -176,7 +177,7 @@ impl World {
     /// let w = {
     ///     let mut w = World::test_world();
     ///     let mut outer = &mut w.objects[0];
-    ///     outer.material.ambient = 1.;
+    ///     let m = outer.material.ambient = 1.;
     ///     let inner = &mut w.objects[1];
     ///     inner.material.ambient = 1.;
     ///     w
@@ -202,6 +203,7 @@ impl World {
     /// ```
     /// use rtchallenge::{
     ///     tuples::{ Tuple},
+    ///     shapes::Shape,
     ///     world::World,
     /// };
     ///