diff --git a/Cargo.lock b/Cargo.lock
index 37381b8..ba36ca2 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -157,9 +157,9 @@ dependencies = [
 
 [[package]]
 name = "jpeg-decoder"
-version = "0.2.6"
+version = "0.2.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9478aa10f73e7528198d75109c8be5cd7d15fb530238040148d5f9a22d4c5b3b"
+checksum = "be7ef4b99870f0c9f2fc2f20dbef72707e2bcca675bb9196734cf433e999b0c5"
 
 [[package]]
 name = "lazy_static"
@@ -169,9 +169,9 @@ checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
 
 [[package]]
 name = "libc"
-version = "0.2.126"
+version = "0.2.125"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "349d5a591cd28b49e1d1037471617a32ddcda5731b99419008085f72d5a53836"
+checksum = "5916d2ae698f6de9bfb891ad7a8d65c09d232dc58cc4ac433c7da3b2fd84bc2b"
 
 [[package]]
 name = "memoffset"
@@ -292,9 +292,9 @@ dependencies = [
 
 [[package]]
 name = "rayon"
-version = "1.5.3"
+version = "1.5.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bd99e5772ead8baa5215278c9b15bf92087709e9c1b2d1f97cdb5a183c933a7d"
+checksum = "fd249e82c21598a9a426a4e00dd7adc1d640b22445ec8545feef801d1a74c221"
 dependencies = [
  "autocfg",
  "crossbeam-deque",
@@ -304,9 +304,9 @@ dependencies = [
 
 [[package]]
 name = "rayon-core"
-version = "1.9.3"
+version = "1.9.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "258bcdb5ac6dad48491bb2992db6b7cf74878b0384908af124823d118c99683f"
+checksum = "9f51245e1e62e1f1629cbfec37b5793bbabcaeb90f30e94d2ba03564687353e4"
 dependencies = [
  "crossbeam-channel",
  "crossbeam-deque",
diff --git a/src/hittable_list.rs b/src/hittable_list.rs
index 5c3d206..6a877f8 100644
--- a/src/hittable_list.rs
+++ b/src/hittable_list.rs
@@ -1,16 +1,15 @@
 use super::HitRecord;
 use super::Hittable;
 use super::Ray;
-use super::Arc;
 
 pub struct HittableList {
-    objects: Vec<Arc<dyn Hittable>>,
+    objects: Vec<Box<dyn Hittable>>,
 }
 
 impl HittableList {
     pub fn new() -> Self {
         HittableList {
-            objects: Vec::<Arc<dyn Hittable>>::new(),
+            objects: Vec::<Box<dyn Hittable>>::new(),
         }
     }
 
@@ -18,16 +17,10 @@ impl HittableList {
         self.objects.clear();
     }
 
-    pub fn add(&mut self, obj: Arc<dyn Hittable>) {
+    pub fn add(&mut self, obj: Box<dyn Hittable>) {
         self.objects.push(obj);
     }
 
-    pub fn clone(&self) -> Self {
-        HittableList {
-            objects : self.objects.clone()
-        }
-    }
-
     pub fn hit(&self, r: &Ray, t_min: f64, t_max: f64, rec: &mut HitRecord) -> bool {
         let mut hit_anything = false;
         let mut closest_so_far = t_max;
diff --git a/src/main.rs b/src/main.rs
index 2109031..19f9406 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -9,7 +9,6 @@ mod utility;
 mod vec3;
 
 use std::env;
-use std::sync::Arc;
 //use std::fs::File;
 //use std::io::BufWriter;
 //use std::io::Write;
@@ -44,23 +43,23 @@ fn main() {
 
     // World
     let mut world = HittableList::new();
-    world.add(Arc::<Sphere>::new(Sphere::new(
+    world.add(Box::<Sphere>::new(Sphere::new(
         Point3::new(0.0, 0.0, -1.0),
         0.5,
     )));
-    world.add(Arc::<Sphere>::new(Sphere::new(
+    world.add(Box::<Sphere>::new(Sphere::new(
         Point3::new(0.0, -100.5, -150.0),
         100.0,
     )));
-    world.add(Arc::<Sphere>::new(Sphere::new(
+    world.add(Box::<Sphere>::new(Sphere::new(
         Point3::new(1.0, 0.0, -1.5),
         0.3,
     )));
-    world.add(Arc::<Sphere>::new(Sphere::new(
+    world.add(Box::<Sphere>::new(Sphere::new(
         Point3::new(1.0, 1.1, -1.5),
         0.3,
     )));
-    world.add(Arc::<Sphere>::new(Sphere::new(
+    world.add(Box::<Sphere>::new(Sphere::new(
         Point3::new(-1.0, 1.1, -1.5),
         0.3,
     )));
@@ -68,7 +67,7 @@ fn main() {
     /*
     for i in -15..15 {
         for j in -15..15 {
-            world.add(Arc::<Sphere>::new(Sphere::new(Point3::new(j as f64/6.0 as f64, i as f64/6.0 as f64, -1.5), 0.05)));
+            world.add(Box::<Sphere>::new(Sphere::new(Point3::new(j as f64/6.0 as f64, i as f64/6.0 as f64, -1.5), 0.05)));
         }
     }
     */
@@ -87,11 +86,11 @@ fn main() {
     //let mut file = BufWriter::new(File::create(default_file).unwrap());
     //writeln!(&mut file, "P3\n{image_width} {image_height}\n255\n").unwrap();
 
-    //TODO: // world in vec umwandeln
+    TODO: // world in vec umwandeln
 
     for j in (0..image_height).rev() {
         eprint!("\rScanlines remaining: {j:5}");
-        (0..image_width).into_par_iter().for_each(|i| pixel_color_calc(&mut image, &cam, &world.clone(), j, i, image_width, image_height, samples_per_pixel));
+        (0..image_width).into_par_iter().for_each(|i| pixel_color_calc(&mut image, &cam, &world, j, i, image_width, image_height, samples_per_pixel));
     }
     image.save(default_file).unwrap();
     eprintln!("\nDone!");