diff --git a/raytracer/main.cpp b/raytracer/main.cpp
index 33e8262..af1417a 100644
--- a/raytracer/main.cpp
+++ b/raytracer/main.cpp
@@ -38,35 +38,71 @@ colour ray_colour(const ray& r, const hittable& world, int depth) {
     return (1.0-t)*colour(1.0, 1.0, 1.0) + t*colour(0.5, 0.7, 1.0);
 }
 
+hittable_list random_scene() {
+    hittable_list world;
+
+    auto ground_material = make_shared<lambertian>(colour(0.5, 0.5, 0.5));
+    world.add(make_shared<sphere>(point3(0,-1000,0), 1000, ground_material));
+
+    for (int a = -11; a < 11; a++)
+        for (int b = -11; b < 11; b++) {
+            auto choose_mat = random_double();
+            point3 center(a + 0.9*random_double(), 0.2, b + 0.9*random_double());
+
+            // don't let spheres intersect with each other
+            if ((center - point3(4, 0.2, 0)).length() > 0.9) {
+                shared_ptr<material> sphere_material;
+
+                // diffuse
+                if (choose_mat < 0.8) {
+                    auto albedo = colour::random() * colour::random();
+                    sphere_material = make_shared<lambertian>(albedo);
+                    world.add(make_shared<sphere>(center, 0.2, sphere_material));
+                // metal
+                } else if (choose_mat < 0.95) {
+                    auto albedo = colour::random(0.5, 1);
+                    auto fuzz = random_double(0, 0.5);
+                    sphere_material = make_shared<metal>(albedo, fuzz);
+                    world.add(make_shared<sphere>(center, 0.2, sphere_material));
+                // glass
+                } else {
+                    sphere_material = make_shared<dielectric>(1.5);
+                    world.add(make_shared<sphere>(center, 0.2, sphere_material));
+                }
+            }
+        }
+
+    // three big spheres
+    auto material1 = make_shared<dielectric>(1.5);
+    world.add(make_shared<sphere>(point3(0,1,0), 1.0, material1));
+
+    auto material2 = make_shared<lambertian>(colour(0.4, 0.2, 0.1));
+    world.add(make_shared<sphere>(point3(-4,1,0), 1.0, material2));
+
+    auto material3 = make_shared<metal>(colour(0.7, 0.6, 0.5), 0.0);
+world.add(make_shared<sphere>(point3(4,1,0), 1.0, material3));
+
+    return world;
+}
+
 int main() {
 
     // write output image in ppm
-    const auto aspect_ratio = 16.0 / 9.0;
-    const int image_width = 400;
+    const auto aspect_ratio = 3.0 / 2.0;
+    const int image_width = 1200;
     const int image_height = static_cast<int>(image_width / aspect_ratio);
-    const int samples_per_pixel = 100;
+    const int samples_per_pixel = 1;
     const int max_depth = 50;
 
     // world
-    hittable_list world;
-
-    auto material_ground = make_shared<lambertian>(colour(0.8, 0.8, 0.0));
-    auto material_center = make_shared<lambertian>(colour(0.1, 0.2, 0.5));
-    auto material_left = make_shared<dielectric>(1.5);
-    auto material_right = make_shared<metal>(colour(0.8, 0.6, 0.2), 0.0);
-
-    world.add(make_shared<sphere>(point3(0.0, -100.5, -1.0), 100.0, material_ground));
-    world.add(make_shared<sphere>(point3(0.0, 0.0, -1.0), 0.5, material_center));
-    world.add(make_shared<sphere>(point3(-1.0, 0.0, -1.0), 0.5, material_left));
-    world.add(make_shared<sphere>(point3(-1.0, 0.0, -1.0), -0.45, material_left));
-    world.add(make_shared<sphere>(point3(1.0, 0.0, -1.0), 0.5, material_right));
+    auto world = random_scene();
 
     // camera with depth of field
-    point3 lookfrom(3,3,2);
-    point3 lookat(0,0,-1);
+    point3 lookfrom(13,2,3);
+    point3 lookat(0,0,0);
     vec3 vup(0,1,0);
-    auto dist_to_focus = (lookfrom-lookat).length();
-    auto aperture = 2.0;
+    auto dist_to_focus = 10.0;
+    auto aperture = 0.1;
 
     camera cam(lookfrom, lookat, vup, 20, aspect_ratio, aperture, dist_to_focus);