diff --git a/src/main.rs b/src/main.rs
index 8316762..4cbbd96 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -3,25 +3,59 @@ use indicatif::ProgressIterator;
 use itertools::Itertools;
 use std::{fs, io};
 
-const IMAGE_HEIGHT: u32 = 256;
-const IMAGE_WIDTH: u32 = 256;
+const IMAGE_WIDTH: u32 = 400;
 const MAX_VALUE: u8 = 255;
+const ASPECT_RATIO: f64 = 16.0 / 9.0;
+const IMAGE_HEIGHT: u32 =
+    (IMAGE_WIDTH as f64 / ASPECT_RATIO) as u32;
+const VIEWPORT_HEIGHT: f64 = 2.0;
+const VIEWPORT_WIDTH: f64 = VIEWPORT_HEIGHT
+    * (IMAGE_WIDTH as f64 / IMAGE_HEIGHT as f64);
+const FOCAL_LENGTH: f64 = 1.0;
+const CAMERA_CENTER: DVec3 = DVec3::ZERO;
+
+// Calculate the vectors across the horizontal and down the vertical viewport edges.
+const VIEWPORT_U: DVec3 =
+    DVec3::new(VIEWPORT_WIDTH, 0., 0.);
+const VIEWPORT_V: DVec3 =
+    DVec3::new(0., -VIEWPORT_HEIGHT, 0.);
 
 fn main() -> io::Result<()> {
+    // Calculate the horizontal and vertical delta vectors from pixel to pixel.
+    let pixel_delta_u: DVec3 =
+        VIEWPORT_U / IMAGE_WIDTH as f64;
+    let pixel_delta_v: DVec3 =
+        VIEWPORT_V / IMAGE_HEIGHT as f64;
+
+    // Calculate the location of the upper left pixel.
+    let viewport_upper_left: DVec3 = CAMERA_CENTER
+        - DVec3::new(0., 0., FOCAL_LENGTH)
+        - VIEWPORT_U / 2.
+        - VIEWPORT_V / 2.;
+    let pixel00_loc: DVec3 = viewport_upper_left
+        + 0.5 * (pixel_delta_u + pixel_delta_v);
+
     let pixels = (0..IMAGE_HEIGHT)
         .cartesian_product(0..IMAGE_WIDTH)
         .progress_count(
             IMAGE_HEIGHT as u64 * IMAGE_WIDTH as u64,
         )
         .map(|(y, x)| {
-            let r = x as f64 / (IMAGE_WIDTH - 1) as f64;
-            let g = y as f64 / (IMAGE_HEIGHT - 1) as f64;
-            let b = 0.0;
+            let pixel_center = pixel00_loc
+                + (x as f64 * pixel_delta_u)
+                + (y as f64 * pixel_delta_v);
+            let ray_direction =
+                pixel_center - CAMERA_CENTER;
+            let ray = Ray {
+                origin: CAMERA_CENTER,
+                direction: ray_direction,
+            };
+
+            let pixel_color = ray.color() * 255.0;
+
             format!(
                 "{} {} {}",
-                r * 255.0,
-                g * 255.0,
-                b * 255.0
+                pixel_color.x, pixel_color.y, pixel_color.z
             )
         })
         .join("\n");
@@ -47,4 +81,11 @@ impl Ray {
     fn at(&self, t: f64) -> DVec3 {
         self.origin + t * self.direction
     }
+    fn color(&self) -> DVec3 {
+        let unit_direction: DVec3 =
+            self.direction.normalize();
+        let a = 0.5 * (unit_direction.y + 1.0);
+        return (1.0 - a) * DVec3::new(1.0, 1.0, 1.0)
+            + a * DVec3::new(0.5, 0.7, 1.0);
+    }
 }