diff --git a/in_one_weekend/src/main.zig b/in_one_weekend/src/main.zig
index 85831ab..d5a409a 100644
--- a/in_one_weekend/src/main.zig
+++ b/in_one_weekend/src/main.zig
@@ -18,14 +18,14 @@ const fps = 60;
 
 fn hitSphere(center: Point3, radius: f32, ray: Ray) f32 {
     const ssr = ray.origin.sub(center); // Sphere-space ray, (A - C) in book
-    const a = Vec3.dot(ray.direction, ray.direction);
-    const b = 2.0 * Vec3.dot(ssr, ray.direction);
-    const c = Vec3.dot(ssr, ssr) - (radius * radius);
-    const discriminant = b * b - 4 * a * c;
+    const a = ray.direction.length_squared();
+    const half_b = Vec3.dot(ssr, ray.direction);
+    const c = ssr.length_squared() - (radius * radius);
+    const discriminant = half_b * half_b - a * c;
     if (discriminant < 0) {
         return -1;
     } else {
-        return (-b - std.math.sqrt(discriminant)) / (2 * a);
+        return (-half_b - std.math.sqrt(discriminant)) / a;
     }
 }
 
diff --git a/in_one_weekend/src/vec3.zig b/in_one_weekend/src/vec3.zig
index c0f54dd..bc607b2 100644
--- a/in_one_weekend/src/vec3.zig
+++ b/in_one_weekend/src/vec3.zig
@@ -41,6 +41,10 @@ pub const Vec3 = packed struct {
         return math.sqrt(self.x * self.x + self.y * self.y + self.z * self.z);
     }
 
+    pub fn length_squared(self: Vec3) f32 {
+        return self.x * self.x + self.y * self.y + self.z * self.z;
+    }
+
     pub fn dot(u: Vec3, v: Vec3) f32 {
         return u.x * v.x + u.y * v.y + u.z * v.z;
     }