diff --git a/light/pointlight.cpp b/light/pointlight.cpp
index b443f85..95c6549 100644
--- a/light/pointlight.cpp
+++ b/light/pointlight.cpp
@@ -4,20 +4,24 @@
 PointLight::PointLight(Vector3d const &position, float intensity, Color const &color) : Light(intensity, color), position(position) {}
 
 Light::Illumination PointLight::illuminate(Scene const &scene, Ray const &ray) const {
-  // IMPLEMENT ME
-  // Get the point on the surface
+  Vector3d const target = ray.origin + (ray.length - LGT_EPS) * ray.direction;
 
-  // Create an instance of the Illumination object, fill in the direction (from
-  // surface point to light source)
-  Light::Illumination illum;
+  // Illumination object
+  Illumination illum;
+  illum.direction = normalized(target - this->position);
+
+  // Precompute the distance from the light source
+  float const distance = length(target - this->position);
 
   // Define a secondary ray from the surface point to the light source.
+  Ray lightRay;
+  lightRay.origin = target;
+  lightRay.direction = -illum.direction;
+  lightRay.length = distance - LGT_EPS;
 
-  // If the target is not in shadow... (use scene.findOcclusion())
-
-  // Compute the brightness-color of this light using inverse squared distance
-  // to light source (i.e. 1/(d^2)), the color of this light source and the
-  // intensity
-
+  // If the target is not in shadow...
+  if (!scene.findOcclusion(lightRay))
+    // ... compute the attenuation and light color
+    illum.color = 1.0f / (distance * distance) * this->color * this->intensity;
   return illum;
 }
diff --git a/primitive/box.cpp b/primitive/box.cpp
index 83a2c75..53e626f 100644
--- a/primitive/box.cpp
+++ b/primitive/box.cpp
@@ -13,19 +13,78 @@ Box::Box(Vector3d const &center, Vector3d const &size, std::shared_ptr<Shader> c
 // Primitive functions /////////////////////////////////////////////////////////
 
 bool Box::intersect(Ray &ray) const {
-  // IMPLEMENT ME!
+  // Project the ray onto the box
+  Vector3d const minBounds = this->center - this->size / 2;
+  Vector3d const maxBounds = this->center + this->size / 2;
+  Vector3d t1 = componentQuotient(minBounds - ray.origin, ray.direction);
+  Vector3d t2 = componentQuotient(maxBounds - ray.origin, ray.direction);
 
-  // Determine whether the ray intersects the box
+  // Determine the intersection points (tNear, tFar)
+  // We also have to remember the intersection axes (tNearIndex, tFarIndex)
+  float tNear = -INFINITY;
+  float tFar = +INFINITY;
+  int tNearIndex = 0;
+  int tFarIndex = 0;
+  for (int d = 0; d < 3; ++d) {
+
+    // Test the trivial case (and to avoid division by zero errors)
+    if (ray.direction[d] == 0 && (ray.origin[d] < minBounds[d] || ray.origin[d] > maxBounds[d]))
+      return false;
+
+    // Swap the bounds if necessary
+    if (t1[d] > t2[d])
+      std::swap(t1[d], t2[d]);
+
+    // Check for the near intersection
+    if (t1[d] > tNear) {
+      tNear = t1[d];
+      tNearIndex = d;
+    }
+
+    // Check for the far intersection
+    if (t2[d] < tFar) {
+      tFar = t2[d];
+      tFarIndex = d;
+    }
+
+    // Check whether we missed the box completely
+    if (tFar < 0 || tNear > tFar)
+      return false;
+  }
+
+  // Check whether we are on the outside or on the inside of the box
+  float const t = (tNear >= 0 ? tNear : tFar);
+  int const tIndex = tNear >= 0 ? tNearIndex : tFarIndex;
 
   // Test whether this is the foremost primitive in front of the camera
+  if (ray.length < t)
+    return false;
 
-  // (Optional for now) Calculate the normal
+  // Calculate the normal
+  ray.normal = Vector3d(0, 0, 0);
+  // Flip the normal if we are on the inside
+  ray.normal[tIndex] = std::copysignf(1.0f, ray.direction[tIndex]) * (tNear < 0.0f ? +1.0f : -1.0f);
 
-  // (Optional for now) Calculate the surface position
+  // Calculate the surface position and tangent vector
+  Vector3d const target = ray.origin + t * ray.direction;
+  Vector3d const surface = componentQuotient(target - minBounds, maxBounds - minBounds);
+  if (tIndex == 0) {
+    ray.surface = Vector2d(surface[2], surface[1]);
+    ray.tangent = Vector3d(0, 0, 1);
+  } else if (tIndex == 1) {
+    ray.surface = Vector2d(surface[0], surface[2]);
+    ray.tangent = Vector3d(1, 0, 0);
+  } else {
+    ray.surface = Vector2d(surface[0], surface[1]);
+    ray.tangent = Vector3d(1, 0, 0);
+  }
 
   // Set the new length and the current primitive
+  ray.length = t;
+  ray.primitive = this;
 
-  return false;
+  // True, because the primitive was hit
+  return true;
 }
 
 // Bounding box ////////////////////////////////////////////////////////////////
diff --git a/primitive/infiniteplane.cpp b/primitive/infiniteplane.cpp
index cc02f31..7a9bb42 100644
--- a/primitive/infiniteplane.cpp
+++ b/primitive/infiniteplane.cpp
@@ -27,7 +27,7 @@ bool InfinitePlane::intersect(Ray &ray) const {
     return false;
 
   // Set the normal
-  // IMPLEMENT ME
+  ray.normal = this->normal;
 
   // Set the new length and the current primitive
   ray.length = t;
diff --git a/primitive/sphere.cpp b/primitive/sphere.cpp
index fc4e76e..54cce80 100644
--- a/primitive/sphere.cpp
+++ b/primitive/sphere.cpp
@@ -36,7 +36,8 @@ bool Sphere::intersect(Ray &ray) const {
     return false;
 
   // Calculate the normal
-  // IMPLEMENT ME
+  Vector3d const hitPoint = ray.origin + t * ray.direction;
+  ray.normal = normalized(hitPoint - this->center);
 
   // Calculate the surface position and tangent vector
   float const phi = std::acos(ray.normal.y);
diff --git a/primitive/triangle.cpp b/primitive/triangle.cpp
index ae98206..b98c539 100644
--- a/primitive/triangle.cpp
+++ b/primitive/triangle.cpp
@@ -100,7 +100,7 @@ bool Triangle::intersect(Ray &ray) const {
     return false;
 
   // Calculate the normal
-  // IMPLEMENT ME
+  ray.normal = normalized(crossProduct(edge1, edge2));
 
   // Calculate the surface position
   ray.surface = u * this->surface[1] + v * this->surface[2] + (1 - u - v) * this->surface[0];
diff --git a/shader/mirrorshader.cpp b/shader/mirrorshader.cpp
index 201a532..83703b7 100644
--- a/shader/mirrorshader.cpp
+++ b/shader/mirrorshader.cpp
@@ -4,9 +4,16 @@
 MirrorShader::MirrorShader() {}
 
 Color MirrorShader::shade(Scene const &scene, Ray const &ray) const {
-  // IMPLEMENT ME
   // Calculate the reflection vector
+  Vector3d const reflection = ray.direction - 2 * dotProduct(ray.normal, ray.direction) * ray.normal;
+
   // Create a new reflection ray
+  Ray reflectionRay = ray;
+  reflectionRay.origin = ray.origin + (ray.length - REFR_EPS) * ray.direction;
+  reflectionRay.direction = normalized(reflection);
+  reflectionRay.length = INFINITY;
+  reflectionRay.primitive = nullptr;
+
   // Send the new ray out into the scene and return the result
-  return Color(0, 0, 1);
+  return scene.traceRay(reflectionRay);
 }
diff --git a/shader/refractionshader.cpp b/shader/refractionshader.cpp
index 1dacc1b..80d2124 100644
--- a/shader/refractionshader.cpp
+++ b/shader/refractionshader.cpp
@@ -4,12 +4,48 @@
 RefractionShader::RefractionShader(float indexInside, float indexOutside) : indexInside(indexInside), indexOutside(indexOutside) {}
 
 Color RefractionShader::shade(Scene const &scene, Ray const &ray) const {
-  // IMPLEMENT ME
-  // Calculate the refracted ray using the surface normal vector and
-  // indexInside, indexOutside
-  // Also check for total internal reflection
-  // Send out a new refracted ray into the scene; recursively call traceRay()
-  return Color(1, 0, 0);
+  // Circumvent getting environment map color into the mix
+  if (ray.getRemainingBounces() > 0) {
+    // Get the normal of the primitive which was hit
+    Vector3d normalVector = ray.normal;
+
+    // Calculate the index of refraction
+    float refractiveIndex = indexOutside / indexInside;
+    // What if we are already inside the object?
+    if (dotProduct(normalVector, ray.direction) > 0) {
+      normalVector = -normalVector;
+      refractiveIndex = indexInside / indexOutside;
+    }
+
+    // Using the notation from the lecture
+    float cosineTheta = dotProduct(normalVector, -ray.direction);
+    float cosinePhi = std::sqrt(1 + refractiveIndex * refractiveIndex * (cosineTheta * cosineTheta - 1));
+    // Calculate t, the new ray direction
+    Vector3d t = refractiveIndex * ray.direction + (refractiveIndex * cosineTheta - cosinePhi) * normalVector;
+
+    // Create the refraction ray
+    Ray refractionRay = ray;
+    // Reset the ray
+    refractionRay.length = INFINITY;
+    refractionRay.primitive = nullptr;
+
+    // Check whether it is a refraction.
+    if (dotProduct(t, normalVector) <= 0.0) {
+      refractionRay.origin = ray.origin + (ray.length + REFR_EPS) * ray.direction;
+      refractionRay.direction = normalized(t);
+    } else { // Otherwise, it is a total reflection.
+      refractionRay.origin = ray.origin + (ray.length - REFR_EPS) * ray.direction;
+      // Next we get the reflection vector
+      Vector3d const reflectionVector = ray.direction - 2.0f * dotProduct(normalVector, ray.direction) * normalVector;
+
+      // Change the ray direction and origin
+      refractionRay.direction = normalized(reflectionVector);
+    }
+
+    // Send out a new refracted ray into the scene
+    return scene.traceRay(refractionRay);
+  }
+  return Color(0.0f, 0.0f, 0.0f);
 }
 
 bool RefractionShader::isTransparent() const { return true; }
diff --git a/shader/simpleshadowshader.cpp b/shader/simpleshadowshader.cpp
index ee456c5..74e5ff7 100644
--- a/shader/simpleshadowshader.cpp
+++ b/shader/simpleshadowshader.cpp
@@ -5,8 +5,11 @@
 SimpleShadowShader::SimpleShadowShader(Color const &objectColor) : objectColor(objectColor) {}
 
 Color SimpleShadowShader::shade(Scene const &scene, Ray const &ray) const {
-  // IMPLEMENT ME
-  // loop over all light sources to check for visibility and multiply "light
-  // strength" with this objects albedo (color)
-  return Color(0, 1, 0);
+  Color fragmentColor;
+
+  // Accumulate the light over all light sources
+  for (const auto &light : scene.lights())
+    fragmentColor += light->illuminate(scene, ray).color;
+
+  return fragmentColor * this->objectColor;
 }