diff --git a/primitive/box.cpp b/primitive/box.cpp
index 83a2c75..9780b85 100644
--- a/primitive/box.cpp
+++ b/primitive/box.cpp
@@ -10,22 +10,84 @@ Box::Box(std::shared_ptr<Shader> const &shader) : Primitive(shader), size(Vector
 Box::Box(Vector3d const &center, Vector3d const &size, std::shared_ptr<Shader> const &shader)
     : Primitive(shader), center(center), size(size) {}
 
+// Helper functions /////////////////////////////////////////////////////////
+
+float intersectionParameterDimension(Vector3d bounds, Ray &ray, int dimension)
+{
+    return (bounds[dimension] - ray.origin[dimension]) / ray.direction[dimension];
+}
+
+Vector3d intersectionParameter(Vector3d bounds, Ray &ray)
+{
+    return Vector3d(intersectionParameterDimension(bounds, ray, 0),
+                    intersectionParameterDimension(bounds, ray, 1),
+                    intersectionParameterDimension(bounds, ray, 2));
+}
+
 // Primitive functions /////////////////////////////////////////////////////////
 
-bool Box::intersect(Ray &ray) const {
-  // IMPLEMENT ME!
+bool Box::intersect(Ray &ray) const
+{
+    // IMPLEMENT ME!
 
-  // Determine whether the ray intersects the box
+    // Determine whether the ray intersects the box
 
-  // Test whether this is the foremost primitive in front of the camera
+    Vector3d minBounds(this->minimumBounds(0), this->minimumBounds(1), this->minimumBounds(2));
+    Vector3d maxBounds(this->maximumBounds(0), this->maximumBounds(1), this->maximumBounds(2));
 
-  // (Optional for now) Calculate the normal
+    Vector3d tMin = intersectionParameter(minBounds, ray);
+    Vector3d tMax = intersectionParameter(maxBounds, ray);
 
-  // (Optional for now) Calculate the surface position
+    Vector3d tInAll = Vector3d(std::min(tMin[0], tMax[0]), std::min(tMin[1], tMax[1]), std::min(tMin[2], tMax[2]));
+    Vector3d tOutAll = Vector3d(std::max(tMin[0], tMax[0]), std::max(tMin[1], tMax[1]), std::max(tMin[2], tMax[2]));
 
-  // Set the new length and the current primitive
+    float tIn = std::max(std::max(tInAll[0], tInAll[1]), tInAll[2]);
+    float tOut = std::min(std::min(tOutAll[0], tOutAll[1]), tOutAll[2]);
 
-  return false;
+    if (tIn > tOut || tOut < 0)
+    {
+        return false;
+    }
+
+    float t = tIn;
+
+    // Test whether this is the foremost primitive in front of the camera
+    if (t >= ray.length)
+    {
+        return false;
+    }
+
+    // (Optional for now) Calculate the normal
+    // On what side of the box did the ray hit?
+    Vector3d normal;
+    if (tInAll[0] == tIn)
+    {
+        normal = Vector3d(1, 0, 0);
+    }
+    else if (tInAll[1] == tIn)
+    {
+        normal = Vector3d(0, 1, 0);
+    }
+    else // tInAll[2] == tIn
+    {
+        normal = Vector3d(0, 0, 1);
+    }
+
+    // Make sure sign is correct
+    if (dotProduct(ray.direction, normal) > 0)
+    {
+        normal = -normal;
+    }
+
+    ray.normal = normalized(normal);
+
+    // (Optional for now) Calculate the surface position
+
+    // Set the new length and the current primitive
+    ray.length = t;
+    ray.primitive = this;
+
+    return false;
 }
 
 // Bounding box ////////////////////////////////////////////////////////////////