diff --git a/out.jpg b/out.jpg
index b65225c..5660126 100644
Binary files a/out.jpg and b/out.jpg differ
diff --git a/tinyraytracer.cpp b/tinyraytracer.cpp
index 0b0e42d..385df3a 100644
--- a/tinyraytracer.cpp
+++ b/tinyraytracer.cpp
@@ -5,11 +5,18 @@
 #include <vector>
 #include "geometry.h"
 
+struct Material {
+    Material(const Vec3f &color) : diffuse_color(color) {}
+    Material() : diffuse_color() {}
+    Vec3f diffuse_color;
+};
+
 struct Sphere {
     Vec3f center;
     float radius;
+    Material material;
 
-    Sphere(const Vec3f &c, const float &r) : center(c), radius(r) {}
+    Sphere(const Vec3f &c, const float &r, const Material &m) : center(c), radius(r), material(m) {}
 
     bool ray_intersect(const Vec3f &orig, const Vec3f &dir, float &t0) const {
         Vec3f L = center - orig;
@@ -25,16 +32,32 @@ struct Sphere {
     }
 };
 
-Vec3f cast_ray(const Vec3f &orig, const Vec3f &dir, const Sphere &sphere) {
-    float sphere_dist = std::numeric_limits<float>::max();
-    if (!sphere.ray_intersect(orig, dir, sphere_dist)) {
+bool scene_intersect(const Vec3f &orig, const Vec3f &dir, const std::vector<Sphere> &spheres, Vec3f &hit, Vec3f &N, Material &material) {
+    float spheres_dist = std::numeric_limits<float>::max();
+    for (size_t i=0; i < spheres.size(); i++) {
+        float dist_i;
+        if (spheres[i].ray_intersect(orig, dir, dist_i) && dist_i < spheres_dist) {
+            spheres_dist = dist_i;
+            hit = orig + dir*dist_i;
+            N = (hit - spheres[i].center).normalize();
+            material = spheres[i].material;
+        }
+    }
+    return spheres_dist<1000;
+}
+
+Vec3f cast_ray(const Vec3f &orig, const Vec3f &dir, const std::vector<Sphere> &spheres) {
+    Vec3f point, N;
+    Material material;
+
+    if (!scene_intersect(orig, dir, spheres, point, N, material)) {
         return Vec3f(0.2, 0.7, 0.8); // background color
     }
 
-    return Vec3f(0.4, 0.4, 0.3);
+    return material.diffuse_color;
 }
 
-void render(const Sphere &sphere) {
+void render(const std::vector<Sphere> &spheres) {
     const int width    = 1024;
     const int height   = 768;
     const int fov      = M_PI/2.;
@@ -46,7 +69,7 @@ void render(const Sphere &sphere) {
             float x =  (2*(i + 0.5)/(float)width  - 1)*tan(fov/2.)*width/(float)height;
             float y = -(2*(j + 0.5)/(float)height - 1)*tan(fov/2.);
             Vec3f dir = Vec3f(x, y, -1).normalize();
-            framebuffer[i+j*width] = cast_ray(Vec3f(0,0,0), dir, sphere);
+            framebuffer[i+j*width] = cast_ray(Vec3f(0,0,0), dir, spheres);
         }
     }
 
@@ -62,8 +85,16 @@ void render(const Sphere &sphere) {
 }
 
 int main() {
-    Sphere sphere(Vec3f(-3, 0, -16), 2);
-    render(sphere);
+    Material      ivory(Vec3f(0.4, 0.4, 0.3));
+    Material red_rubber(Vec3f(0.3, 0.1, 0.1));
+
+    std::vector<Sphere> spheres;
+    spheres.push_back(Sphere(Vec3f(-3,    0,   -16), 2,      ivory));
+    spheres.push_back(Sphere(Vec3f(-1.0, -1.5, -12), 2, red_rubber));
+    spheres.push_back(Sphere(Vec3f( 1.5, -0.5, -18), 3, red_rubber));
+    spheres.push_back(Sphere(Vec3f( 7,    5,   -18), 4,      ivory));
+
+    render(spheres);
 
     return 0;
 }