diff --git a/ria-weekend/examples/ppm.rs b/ria-weekend/examples/ppm.rs
index 8422cd0..d0d6bf5 100644
--- a/ria-weekend/examples/ppm.rs
+++ b/ria-weekend/examples/ppm.rs
@@ -27,14 +27,16 @@ fn main() {
         width = input[0];
     }
     let file_name = format!("ppm_sample{}x{}.ppm", width, height);
-    let ppm_sample = ppm::create_sample(height, width);
+    let mut buf = format!("P3\n{} {}\n255\n", width, height);
+
+    ppm::create_sample(&mut buf, height, width);
 
     let mut file = match File::create(&file_name) {
         Ok(file) => file,
         Err(e) => panic!("couldn't create {}: {}", file_name, e.description()),
     };
 
-    match file.write_all(ppm_sample.as_bytes()) {
+    match file.write_all(buf.as_bytes()) {
         Ok(_) => println!("Succesfully wrote to {}", file_name),
         Err(e) => panic!("couldn't write to {}: {}", file_name, e.description()),
     }
diff --git a/ria-weekend/examples/ray_demo.rs b/ria-weekend/examples/ray_demo.rs
new file mode 100644
index 0000000..2d4f2d2
--- /dev/null
+++ b/ria-weekend/examples/ray_demo.rs
@@ -0,0 +1,41 @@
+extern crate ria_weekend;
+
+use ria_weekend::ray;
+use std::error::Error;
+use std::fs::File;
+use std::{io, io::Write};
+
+fn main() {
+    let mut height = 100;
+    let mut width = 200;
+
+    println!("Enter width and height seperated by space");
+
+    let mut input = String::new();
+    io::stdin()
+        .read_line(&mut input)
+        .expect("error in reading input");
+
+    let input = input
+        .trim()
+        .split(" ")
+        .map(|v| v.parse::<u32>().expect("error in parsing input"))
+        .collect::<Vec<u32>>();
+
+    if input.len() >= 2 {
+        height = input[1];
+        width = input[0];
+    }
+    let file_name = format!("ray_demo{}x{}.ppm", width, height);
+    let mut buf = format!("P3\n{} {}\n255\n", width, height);
+    let mut file = match File::create(&file_name) {
+        Ok(file) => file,
+        Err(e) => panic!("couldn't create {}: {}", file_name, e.description()),
+    };
+    ray::create_ray_demo(&mut buf, width, height);
+
+    match file.write_all(buf.as_bytes()) {
+        Ok(_) => println!("Succesfully wrote to {}", file_name),
+        Err(e) => panic!("couldn't write to {}: {}", file_name, e.description()),
+    }
+}
diff --git a/ria-weekend/src/ppm.rs b/ria-weekend/src/ppm.rs
index 39b7133..66025f1 100644
--- a/ria-weekend/src/ppm.rs
+++ b/ria-weekend/src/ppm.rs
@@ -1,7 +1,6 @@
 use crate::vec3::Vec3;
 
-pub fn create_sample(h: u32, w: u32) -> String {
-    let mut buf = format!("P3\n{} {}\n255\n", w, h);
+pub fn create_sample(buf: &mut String, h: u32, w: u32)  {
     for j in (0..h).rev() {
         for i in 0..w {
             let color = Vec3::new((i as f32) / (w as f32), (j as f32) / (h as f32), 0.5_f32);
@@ -12,5 +11,4 @@ pub fn create_sample(h: u32, w: u32) -> String {
             buf.push_str(&format!("{} {} {}\n", ir, ig, ib));
         }
     }
-    buf
 }
diff --git a/ria-weekend/src/ray.rs b/ria-weekend/src/ray.rs
index 39b763f..6a285ba 100644
--- a/ria-weekend/src/ray.rs
+++ b/ria-weekend/src/ray.rs
@@ -6,19 +6,45 @@ pub struct Ray {
 }
 
 impl Ray {
-    pub const fn new(a: Vec3, b: Vec3) -> Ray {
+    pub fn new(a: Vec3, b: Vec3) -> Ray {
         Ray { a, b }
     }
-
-    pub const fn origin(&self) -> &Vec3 {
-        return &self.a;
+    pub fn origin(&self) -> Vec3 {
+        return self.a;
     }
-
-    pub const fn direction(&self) -> &Vec3 {
-        return &self.b;
+    pub fn direction(&self) -> Vec3 {
+        return self.b;
     }
-
-    pub const fn point_at_diameter(&self, t: f32) -> Vec3 {
-        return self.a  + t * self.b;
+    pub fn point_at_parameter(&self, t: f32) -> Vec3 {
+        return self.a + self.b * t;
+    }
+}
+
+fn color(ray: Ray) -> Vec3 {
+    let unit_direction = ray.direction().unit_vector();
+    let t = 0.5 * (unit_direction.y() + 1.0);
+    return Vec3::new(1.0, 1.0, 1.0) * (1.0 - t) + Vec3::new(0.5, 0.7, 1.0) * t;
+}
+
+pub fn create_ray_demo(buf: &mut String, w: u32, h: u32) {
+    let lower_left_corner = Vec3::new(-2.0, -1.0, -1.0);
+    let horizontal = Vec3::new(4.0, 0.0, 0.0);
+    let vertical = Vec3::new(0.0, 2.0, 0.0);
+    let origin = Vec3::new(0.0, 0.0, 0.0);
+
+    for j in (0..h).rev() {
+        for i in 0..w {
+            let u = i as f32 / w as f32;
+            let v = j as f32 / h as f32;
+
+            let ray = Ray::new(origin, lower_left_corner + horizontal * u + vertical * v);
+
+            let color = color(ray);
+            let ir = (255.99 * color[0]) as u32;
+            let ig = (255.99 * color[1]) as u32;
+            let ib = (255.99 * color[2]) as u32;
+            let output = format!("{} {} {}\n", ir, ig, ib);
+            buf.push_str(&output);
+        }
     }
 }
diff --git a/ria-weekend/src/vec3.rs b/ria-weekend/src/vec3.rs
index 99e4581..99fcffc 100644
--- a/ria-weekend/src/vec3.rs
+++ b/ria-weekend/src/vec3.rs
@@ -1,5 +1,6 @@
-use std::ops::{Add, Div, Index, Mul, Sub};
+use std::ops::{Add, Div, Index, IndexMut, Mul, MulAssign, Sub};
 
+#[derive(Debug, Copy, Clone)]
 pub struct Vec3 {
     inner: [f32; 3],
 }
@@ -10,50 +11,54 @@ impl Vec3 {
     }
 
     pub fn x(&self) -> f32 {
-        self.inner[0]
+        self[0]
     }
     pub fn y(&self) -> f32 {
-        self.inner[1]
+        self[1]
     }
     pub fn z(&self) -> f32 {
-        self.inner[2]
+        self[2]
     }
     pub fn r(&self) -> f32 {
-        self.inner[0]
+        self[0]
     }
     pub fn g(&self) -> f32 {
-        self.inner[1]
+        self[1]
     }
     pub fn b(&self) -> f32 {
-        self.inner[2]
+        self[2]
     }
 
     pub fn length(&self) -> f32 {
-        (self.inner[0] * self.inner[0]
-            + self.inner[1] * self.inner[1]
-            + self.inner[2] * self.inner[2])
-            .sqrt()
+        self.sq_len().sqrt()
     }
 
     pub fn sq_len(&self) -> f32 {
-        self.inner[0] * self.inner[0]
-            + self.inner[1] * self.inner[1]
-            + self.inner[2] * self.inner[2]
+        self[0] * self[0]
+            + self[1] * self[1]
+            + self[2] * self[2]
     }
 
     pub fn dot(&self, v: &Vec3) -> f32 {
-        self.inner[0] * v.inner[0] + self.inner[1] * v.inner[1] + self.inner[2] * v.inner[2]
+        self[0] * v[0] + self[1] * v[1] + self[2] * v[2]
     }
 
     pub fn cross(&self, v: &Vec3) -> Vec3 {
         Vec3 {
             inner: [
-                self.inner[1] * v.inner[2] - self.inner[2] * v.inner[1],
-                self.inner[2] * v.inner[0] - self.inner[0] * v.inner[2],
-                self.inner[0] * v.inner[1] - self.inner[1] * v.inner[0],
+                self[1] * v[2] - self[2] * v[1],
+                self[2] * v[0] - self[0] * v[2],
+                self[0] * v[1] - self[1] * v[0],
             ],
         }
     }
+
+    pub fn unit_vector(&self) -> Vec3 {
+        let length = self.length();
+        Vec3 {
+            inner: [self[0] / length, self[1] / length, self[2] / length],
+        }
+    }
 }
 
 impl Add for Vec3 {
@@ -62,9 +67,9 @@ impl Add for Vec3 {
     fn add(self, o: Vec3) -> Vec3 {
         Vec3 {
             inner: [
-                self.inner[0] + o.inner[0],
-                self.inner[1] + o.inner[1],
-                self.inner[2] + o.inner[2],
+                self[0] + o[0],
+                self[1] + o[1],
+                self[2] + o[2],
             ],
         }
     }
@@ -76,34 +81,35 @@ impl Sub for Vec3 {
     fn sub(self, o: Vec3) -> Vec3 {
         Vec3 {
             inner: [
-                self.inner[0] - o.inner[0],
-                self.inner[1] - o.inner[1],
-                self.inner[2] - o.inner[2],
+                self[0] - o[0],
+                self[1] - o[1],
+                self[2] - o[2],
             ],
         }
     }
 }
 
-impl Mul<Vec3> for Vec3 {
-    type Output = Vec3;
+impl MulAssign<Vec3> for Vec3 {
+    fn mul_assign(&mut self, o: Vec3) {
+        self[0] *= o[0];
+        self[1] *= o[1];
+        self[2] *= o[2];
+    }
+}
 
-    fn mul(self, o: Vec3) -> Vec3 {
-        Vec3 {
-            inner: [
-                self.inner[0] * o.inner[0],
-                self.inner[1] * o.inner[1],
-                self.inner[2] * o.inner[2],
-            ],
-        }
+impl MulAssign<f32> for Vec3 {
+    fn mul_assign(&mut self, o: f32) {
+        self[0] *= o;
+        self[1] *= o;
+        self[2] *= o;
     }
 }
 
 impl Mul<f32> for Vec3 {
     type Output = Vec3;
-
     fn mul(self, o: f32) -> Vec3 {
         Vec3 {
-            inner: [self.inner[0] * o, self.inner[1] * o, self.inner[2] * o],
+            inner: [self[0] * o, self[1] * o, self[2] * o],
         }
     }
 }
@@ -114,9 +120,9 @@ impl Div<Vec3> for Vec3 {
     fn div(self, o: Vec3) -> Vec3 {
         Vec3 {
             inner: [
-                self.inner[0] / o.inner[0],
-                self.inner[1] / o.inner[1],
-                self.inner[2] / o.inner[2],
+                self[0] / o[0],
+                self[1] / o[1],
+                self[2] / o[2],
             ],
         }
     }
@@ -128,7 +134,7 @@ impl Div<f32> for Vec3 {
     fn div(self, o: f32) -> Vec3 {
         let o = 1.0 / o;
         Vec3 {
-            inner: [self.inner[0] * o, self.inner[1] * o, self.inner[2] * o],
+            inner: [self[0] * o, self[1] * o, self[2] * o],
         }
     }
 }
@@ -140,3 +146,9 @@ impl Index<usize> for Vec3 {
         &self.inner[q]
     }
 }
+
+impl IndexMut<usize> for Vec3 {
+    fn index_mut(&mut self, q: usize) -> &mut f32 {
+        &mut self.inner[q]
+    }
+}