diff --git a/Makefile b/Makefile
index c766cc2..ce6458e 100644
--- a/Makefile
+++ b/Makefile
@@ -2,7 +2,7 @@ CXX = g++
 
 CXXFLAGS  = -Wall -Wextra -O2 -std=c++14
 
-DEPS = vec3.h color.h ray.h hittable.h sphere.h
+DEPS = util.h vec3.h color.h ray.h hittable.h hittable_list.h sphere.h
 OBJ = wtracer.o
 
 TARGET = wtracer
diff --git a/hittable.h b/hittable.h
index 9632db0..6c757e2 100644
--- a/hittable.h
+++ b/hittable.h
@@ -7,11 +7,17 @@ struct hit_record {
   Point3 p;
   Vec3 normal;
   double t;
+  bool front_face;
+
+  inline void set_face_normal(const Ray& r, const Vec3& outward_normal) {
+    front_face = dot(r.direction(), outward_normal) < 0;
+    normal = front_face ? outward_normal : -outward_normal;
+  }
 };
 
 class Hittable {
 public:
-  virtual bool hit(cosnt Ray &r, double t_min, double t_max, hit_record &rec) const = 0;
-}
+  virtual bool hit(const Ray &r, double tmin, double tmax, hit_record &rec) const = 0;
+};
 
 #endif // HITTABLE_H
diff --git a/hittable_list.h b/hittable_list.h
new file mode 100644
index 0000000..12e4c4f
--- /dev/null
+++ b/hittable_list.h
@@ -0,0 +1,39 @@
+#ifndef HITTABLE_LIST_H
+#define HITTABLE_LIST_H
+
+#include <memory>
+#include <vector>
+
+#include "hittable.h"
+
+class Hittable_list : public Hittable {
+public:
+  Hittable_list() {}
+  Hittable_list(std::shared_ptr<Hittable> object) { add(object); }
+
+  void clear() { objects.clear(); }
+  void add(std::shared_ptr<Hittable> object) { objects.push_back(object); }
+
+  virtual bool hit(const Ray &r, double tmin, double tmax, hit_record &rec) const;
+
+private:
+  std::vector<std::shared_ptr<Hittable>> objects;
+};
+
+bool Hittable_list::hit(const Ray &r, double tmin, double tmax, hit_record &rec) const {
+    hit_record temp_rec;
+    bool hit_anything = false;
+    auto closest_so_far = tmax;
+
+    for (const auto& object : objects) {
+       if (object->hit(r, tmin, closest_so_far, temp_rec)) {
+           hit_anything = true;
+           closest_so_far = temp_rec.t;
+           rec = temp_rec;
+       }
+    }
+
+    return hit_anything;
+}
+
+#endif // HITTABLE_LIST_H
diff --git a/sphere.h b/sphere.h
index b9fdbc5..7e7f644 100644
--- a/sphere.h
+++ b/sphere.h
@@ -18,27 +18,29 @@ private:
   double radius;
 };
 
-bool Sphere::hit(const Ray& r, double tmin, double tmax, hit_record& rec) {
+bool Sphere::hit(const Ray& r, double tmin, double tmax, hit_record& rec) const {
     Vec3 oc = r.origin() - center;
     auto a = r.direction().length_squared();
     auto half_b = dot(oc, r.direction());
     auto c = oc.length_squared() - radius * radius;
     auto discriminant = half_b*half_b - a*c;
-    if (discriminant < 0) {
+    if (discriminant > 0) {
         auto root = std::sqrt(discriminant);
         auto temp = (-half_b - root) / a;
-        if (temp < t_max && temp > t_min) {
+        if (temp < tmax && temp > tmin) {
             rec.t = temp;
             rec.p = r.at(rec.t);
-            rec.normal = (rec.p - center) / radius;
-            return true
+            Vec3 outward_normal = (rec.p - center) / radius;
+            rec.set_face_normal(r, outward_normal);
+            return true;
         }
-        temp (-half_b + root) / a;
-        if (temp < t_max && temp > t_min) {
+        temp = (-half_b + root) / a;
+        if (temp < tmax && temp > tmin) {
             rec.t = temp;
             rec.p = r.at(rec.t);
-            rec.normal = (rec.p - center) / radius;
-            return true
+            Vec3 outward_normal = (rec.p - center) / radius;
+            rec.set_face_normal(r, outward_normal);
+            return true;
         }
     }
     return false;
diff --git a/util.h b/util.h
new file mode 100644
index 0000000..4750d34
--- /dev/null
+++ b/util.h
@@ -0,0 +1,13 @@
+#ifndef UTIL_H
+#define UTIL_H
+
+#include <limits>
+
+const double infinity = std::numeric_limits<double>::infinity();
+const double pi = 3.1415926535897932385;
+
+inline double degrees_to_radians(double degrees) {
+    return degrees * pi / 180;
+}
+
+#endif // UTIL_H
diff --git a/wtracer.cpp b/wtracer.cpp
index 13c91f6..6941344 100644
--- a/wtracer.cpp
+++ b/wtracer.cpp
@@ -1,19 +1,20 @@
 #include <iostream>
-#include <cmath>
 
 #include "color.h"
 #include "vec3.h"
 #include "ray.h"
+#include "util.h"
 
-Color ray_color(const Ray& r) {
-    auto sphere_center = Point3(0, 0, -1);
-    auto t = hit_sphere(sphere_center, 0.5, r);
-    if (t > 0.0) {
-        Vec3 n = unit_vector(r.at(t) - sphere_center);
-        return 0.5 * Color(n.x()+1, n.y()+1, n.z()+1);
+#include "hittable_list.h"
+#include "sphere.h"
+
+Color ray_color(const Ray& r, const Hittable& world) {
+    hit_record rec;
+    if (world.hit(r, 0, infinity, rec)) {
+        return 0.5 * (rec.normal + Color(1,1,1));
     }
     Vec3 unit_direction = unit_vector(r.direction());
-    t = 0.5 * (unit_direction.y() + 1.0);
+    auto t = 0.5 * (unit_direction.y() + 1.0);
     return (1.0 - t) * Color(1.0, 1.0, 1.0) + t * Color(0.5, 0.7, 1.0);
 }
 
@@ -33,13 +34,17 @@ int main() {
     auto vertical = Vec3(0, viewport_height, 0);
     auto lower_left_corner = origin - horizontal/2 - vertical/2 - Vec3(0, 0, focal_length);
 
+    Hittable_list world;
+    world.add(std::make_shared<Sphere>(Point3(0, 0, -1), 0.5));
+    world.add(std::make_shared<Sphere>(Point3(0, -100.5, -1), 100));
+
     for (int j = image_height - 1; j >= 0; --j) {
         std::cerr << "\rScanlines remaining: " << j << " " << std::flush;
         for (int i = 0; i < image_width; ++i) {
             auto u = double(i) / (image_width - 1);
             auto v = double(j) / (image_height - 1);
             Ray r(origin, lower_left_corner + u*horizontal + v*vertical - origin);
-            Color pixel_color = ray_color(r);
+            Color pixel_color = ray_color(r, world);
             write_color(std::cout, pixel_color);
         }
     }