diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5d4d782..c6b9984 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -40,6 +40,7 @@ $<IF:$<CONFIG:Debug>,-Og,-fno-delete-null-pointer-checks -fno-strict-overflow -f
 add_executable(UnitTest src/test.cpp)
 target_link_libraries(UnitTest SC_SeparatingAxisCollisionDetection)
 target_include_directories(UnitTest PUBLIC "${CMAKE_CURRENT_SOURCE_DIR}/src")
+target_compile_features(UnitTest PUBLIC cxx_std_20)
 
 target_compile_options(UnitTest PUBLIC
 $<IF:$<CONFIG:Debug>,-Og,-fno-delete-null-pointer-checks -fno-strict-overflow -fno-strict-aliasing -ftrivial-auto-var-init=zero>
diff --git a/src/sd_sacd.cpp b/src/sd_sacd.cpp
index ebafe61..90e8e9d 100644
--- a/src/sd_sacd.cpp
+++ b/src/sd_sacd.cpp
@@ -2,6 +2,126 @@
 
 // Standard library includes.
 #include <cmath>
+#include <stdfloat>
+#include <vector>
+
+// =============================================================================
+// Private Helpers BEGIN
+// =============================================================================
+
+SC_SACD_Vec3 operator+(const SC_SACD_Vec3 &a, const SC_SACD_Vec3 &b) {
+  return SC_SACD_Vec3{a.x + b.x, a.y + b.y, a.z + b.z};
+}
+
+std::vector<SC_SACD_Vec3> SC_SACD_Get_Box_Normals(
+    const SC_SACD_Generic_Box *box) {
+  std::vector<SC_SACD_Vec3> normals;
+
+  normals.emplace_back(SC_SACD_Vec3{1.0F, 0.0F, 0.0F});
+  normals.back() = SC_SACD_Vec3_Rotate(normals.back(), box->x_radians,
+                                       box->y_radians, box->z_radians);
+
+  normals.emplace_back(SC_SACD_Vec3{0.0F, 1.0F, 0.0F});
+  normals.back() = SC_SACD_Vec3_Rotate(normals.back(), box->x_radians,
+                                       box->y_radians, box->z_radians);
+
+  normals.emplace_back(SC_SACD_Vec3{0.0F, 0.0F, 1.0F});
+  normals.back() = SC_SACD_Vec3_Rotate(normals.back(), box->x_radians,
+                                       box->y_radians, box->z_radians);
+
+  // Not normalizing the normals on purpose for optimization. (No unit vectors.)
+  return normals;
+}
+
+std::vector<SC_SACD_Vec3> SC_SACD_Get_Box_Corners(
+    const SC_SACD_Generic_Box *box) {
+  std::vector<SC_SACD_Vec3> corners;
+
+  SC_SACD_Vec3 pos{box->x, box->y, box->z};
+
+  corners.push_back(
+      SC_SACD_Vec3_Rotate(SC_SACD_Vec3{-box->width / 2.0F, -box->height / 2.0F,
+                                       -box->depth / 2.0F},
+                          box->x_radians, box->y_radians, box->z_radians) +
+      pos);
+
+  corners.push_back(
+      SC_SACD_Vec3_Rotate(SC_SACD_Vec3{box->width / 2.0F, -box->height / 2.0F,
+                                       -box->depth / 2.0F},
+                          box->x_radians, box->y_radians, box->z_radians) +
+      pos);
+
+  corners.push_back(
+      SC_SACD_Vec3_Rotate(SC_SACD_Vec3{-box->width / 2.0F, box->height / 2.0F,
+                                       -box->depth / 2.0F},
+                          box->x_radians, box->y_radians, box->z_radians) +
+      pos);
+
+  corners.push_back(
+      SC_SACD_Vec3_Rotate(SC_SACD_Vec3{box->width / 2.0F, box->height / 2.0F,
+                                       -box->depth / 2.0F},
+                          box->x_radians, box->y_radians, box->z_radians) +
+      pos);
+
+  corners.push_back(
+      SC_SACD_Vec3_Rotate(SC_SACD_Vec3{-box->width / 2.0F, -box->height / 2.0F,
+                                       box->depth / 2.0F},
+                          box->x_radians, box->y_radians, box->z_radians) +
+      pos);
+
+  corners.push_back(
+      SC_SACD_Vec3_Rotate(SC_SACD_Vec3{box->width / 2.0F, -box->height / 2.0F,
+                                       box->depth / 2.0F},
+                          box->x_radians, box->y_radians, box->z_radians) +
+      pos);
+
+  corners.push_back(
+      SC_SACD_Vec3_Rotate(SC_SACD_Vec3{-box->width / 2.0F, box->height / 2.0F,
+                                       box->depth / 2.0F},
+                          box->x_radians, box->y_radians, box->z_radians) +
+      pos);
+
+  corners.push_back(
+      SC_SACD_Vec3_Rotate(SC_SACD_Vec3{box->width / 2.0F, box->height / 2.0F,
+                                       box->depth / 2.0F},
+                          box->x_radians, box->y_radians, box->z_radians) +
+      pos);
+
+  return corners;
+}
+
+struct SC_SACD_MinMax {
+  float min, max;
+};
+
+std::vector<SC_SACD_MinMax> SC_SACD_Get_Box_MinMax(
+    const SC_SACD_Generic_Box *box, const std::vector<SC_SACD_Vec3> &normals) {
+  std::vector<SC_SACD_MinMax> minmaxes;
+
+  std::vector<SC_SACD_Vec3> corners = SC_SACD_Get_Box_Corners(box);
+
+  // Assuming normals are not normalized, and will not normalize anyway.
+  // MinMax count should be same as normals count.
+  for (const auto &normal : normals) {
+    SC_SACD_MinMax minmax{INFINITY, -INFINITY};
+    for (const auto &corner : corners) {
+      float projected = SC_SACD_Dot_Product(corner, normal);
+      if (projected > minmax.max) {
+        minmax.max = projected;
+      }
+      if (projected < minmax.min) {
+        minmax.min = projected;
+      }
+    }
+    minmaxes.push_back(minmax);
+  }
+
+  return minmaxes;
+}
+
+// =============================================================================
+// Private Helpers END
+// =============================================================================
 
 int SC_SACD_AABB_Box_Collision(const SC_SACD_AABB_Box *a,
                                const SC_SACD_AABB_Box *b) {
@@ -27,8 +147,25 @@ int SC_SACD_AABB_Box_Collision(const SC_SACD_AABB_Box *a,
 
 int SC_SACD_Generic_Box_Collision(const SC_SACD_Generic_Box *a,
                                   const SC_SACD_Generic_Box *b) {
-  // TODO
-  return 0;
+  // Get all normals.
+  std::vector<SC_SACD_Vec3> normals = SC_SACD_Get_Box_Normals(a);
+  for (const auto &normal : SC_SACD_Get_Box_Normals(b)) {
+    normals.push_back(normal);
+  }
+
+  // Get all minmaxes.
+  std::vector<SC_SACD_MinMax> minmaxes_a = SC_SACD_Get_Box_MinMax(a, normals);
+  std::vector<SC_SACD_MinMax> minmaxes_b = SC_SACD_Get_Box_MinMax(b, normals);
+
+  // Check minmaxes.
+  for (unsigned int i = 0; i < normals.size(); ++i) {
+    if (minmaxes_a[i].max < minmaxes_b[i].min ||
+        minmaxes_b[i].max < minmaxes_a[i].min) {
+      return 0;
+    }
+  }
+
+  return 1;
 }
 
 int SC_SACD_AABB_Generic_Box_Collision(const SC_SACD_AABB_Box *a,
diff --git a/src/test.cpp b/src/test.cpp
index 1ddcd28..124a5a6 100644
--- a/src/test.cpp
+++ b/src/test.cpp
@@ -1,4 +1,5 @@
 #include <iostream>
+#include <numbers>
 
 static int checks_checked = 0;
 static int checks_passed = 0;
@@ -28,57 +29,107 @@ static int checks_passed = 0;
 
 int main() {
   // Test 2D AABB.
-  SC_SACD_AABB_Box a{0.0F, 0.0F, 0.0F, 1.0F, 1.0F, 1.0F};
-  SC_SACD_AABB_Box b{2.0F, 0.0F, 0.0F, 1.0F, 1.0F, 1.0F};
+  {
+    SC_SACD_AABB_Box a{0.0F, 0.0F, 0.0F, 1.0F, 1.0F, 1.0F};
+    SC_SACD_AABB_Box b{2.0F, 0.0F, 0.0F, 1.0F, 1.0F, 1.0F};
 
-  CHECK_FALSE(SC_SACD_AABB_Box_Collision(&a, &b));
+    CHECK_FALSE(SC_SACD_AABB_Box_Collision(&a, &b));
 
-  b.x = -2.0F;
-  CHECK_FALSE(SC_SACD_AABB_Box_Collision(&a, &b));
+    b.x = -2.0F;
+    CHECK_FALSE(SC_SACD_AABB_Box_Collision(&a, &b));
 
-  b.x = 0.5F;
-  CHECK_TRUE(SC_SACD_AABB_Box_Collision(&a, &b));
-  b.x = -0.5F;
-  CHECK_TRUE(SC_SACD_AABB_Box_Collision(&a, &b));
+    b.x = 0.5F;
+    CHECK_TRUE(SC_SACD_AABB_Box_Collision(&a, &b));
+    b.x = -0.5F;
+    CHECK_TRUE(SC_SACD_AABB_Box_Collision(&a, &b));
 
-  b.x = 0.0F;
-  b.y = 2.0F;
-  CHECK_FALSE(SC_SACD_AABB_Box_Collision(&a, &b));
-  b.y = -2.0F;
-  CHECK_FALSE(SC_SACD_AABB_Box_Collision(&a, &b));
+    b.x = 0.0F;
+    b.y = 2.0F;
+    CHECK_FALSE(SC_SACD_AABB_Box_Collision(&a, &b));
+    b.y = -2.0F;
+    CHECK_FALSE(SC_SACD_AABB_Box_Collision(&a, &b));
 
-  b.y = 0.5F;
-  CHECK_TRUE(SC_SACD_AABB_Box_Collision(&a, &b));
-  b.y = -0.5F;
-  CHECK_TRUE(SC_SACD_AABB_Box_Collision(&a, &b));
+    b.y = 0.5F;
+    CHECK_TRUE(SC_SACD_AABB_Box_Collision(&a, &b));
+    b.y = -0.5F;
+    CHECK_TRUE(SC_SACD_AABB_Box_Collision(&a, &b));
 
-  b.y = 0.0F;
-  b.z = 2.0F;
-  CHECK_FALSE(SC_SACD_AABB_Box_Collision(&a, &b));
+    b.y = 0.0F;
+    b.z = 2.0F;
+    CHECK_FALSE(SC_SACD_AABB_Box_Collision(&a, &b));
 
-  b.z = -2.0F;
-  CHECK_FALSE(SC_SACD_AABB_Box_Collision(&a, &b));
+    b.z = -2.0F;
+    CHECK_FALSE(SC_SACD_AABB_Box_Collision(&a, &b));
 
-  b.z = 0.5F;
-  CHECK_TRUE(SC_SACD_AABB_Box_Collision(&a, &b));
+    b.z = 0.5F;
+    CHECK_TRUE(SC_SACD_AABB_Box_Collision(&a, &b));
 
-  b.z = -0.5F;
-  CHECK_TRUE(SC_SACD_AABB_Box_Collision(&a, &b));
+    b.z = -0.5F;
+    CHECK_TRUE(SC_SACD_AABB_Box_Collision(&a, &b));
 
-  b.z = 0.0F;
-  b.x = 0.5F;
-  b.y = 2.0F;
-  CHECK_FALSE(SC_SACD_AABB_Box_Collision(&a, &b));
+    b.z = 0.0F;
+    b.x = 0.5F;
+    b.y = 2.0F;
+    CHECK_FALSE(SC_SACD_AABB_Box_Collision(&a, &b));
 
-  b.y = -2.0F;
-  CHECK_FALSE(SC_SACD_AABB_Box_Collision(&a, &b));
+    b.y = -2.0F;
+    CHECK_FALSE(SC_SACD_AABB_Box_Collision(&a, &b));
 
-  b.x = -0.5F;
-  b.y = 2.0F;
-  CHECK_FALSE(SC_SACD_AABB_Box_Collision(&a, &b));
+    b.x = -0.5F;
+    b.y = 2.0F;
+    CHECK_FALSE(SC_SACD_AABB_Box_Collision(&a, &b));
 
-  b.y = -2.0F;
-  CHECK_FALSE(SC_SACD_AABB_Box_Collision(&a, &b));
+    b.y = -2.0F;
+    CHECK_FALSE(SC_SACD_AABB_Box_Collision(&a, &b));
+  }
+
+  // Test Separating_Axis_Collision check.
+  {
+    SC_SACD_Generic_Box a{0.0F, 0.0F, 0.0F, 1.0F, 1.0F, 1.0F, 0.0F, 0.0F, 0.0F};
+    SC_SACD_Generic_Box b{0.0F, 0.0F, 0.0F, 1.0F, 1.0F, 1.0F, 0.0F, 0.0F, 0.0F};
+
+    CHECK_TRUE(SC_SACD_Generic_Box_Collision(&a, &b));
+
+    b.x = 1.1F;
+    CHECK_FALSE(SC_SACD_Generic_Box_Collision(&a, &b));
+    b.x = -1.1F;
+    CHECK_FALSE(SC_SACD_Generic_Box_Collision(&a, &b));
+
+    a.z_radians = std::numbers::pi_v<float> / 4.0F;
+    b.z_radians = a.z_radians;
+    CHECK_TRUE(SC_SACD_Generic_Box_Collision(&a, &b));
+    b.x = 1.1F;
+    CHECK_TRUE(SC_SACD_Generic_Box_Collision(&a, &b));
+
+    b.x = 0.0F;
+    b.y = 1.1F;
+    a.z_radians = 0.0F;
+    b.z_radians = 0.0F;
+    CHECK_FALSE(SC_SACD_Generic_Box_Collision(&a, &b));
+    b.y = -1.1F;
+    CHECK_FALSE(SC_SACD_Generic_Box_Collision(&a, &b));
+
+    a.z_radians = std::numbers::pi_v<float> / 4.0F;
+    b.z_radians = a.z_radians;
+    CHECK_TRUE(SC_SACD_Generic_Box_Collision(&a, &b));
+    b.y = 1.1F;
+    CHECK_TRUE(SC_SACD_Generic_Box_Collision(&a, &b));
+
+    b.y = 0.0F;
+    a.z_radians = 0.0F;
+    b.z_radians = 0.0F;
+
+    b.z = 1.1F;
+    CHECK_FALSE(SC_SACD_Generic_Box_Collision(&a, &b));
+    b.z = -1.1F;
+    CHECK_FALSE(SC_SACD_Generic_Box_Collision(&a, &b));
+
+    a.y_radians = std::numbers::pi_v<float> / 4.0F;
+    b.y_radians = a.y_radians;
+    CHECK_TRUE(SC_SACD_Generic_Box_Collision(&a, &b));
+    b.z = 1.1F;
+    CHECK_TRUE(SC_SACD_Generic_Box_Collision(&a, &b));
+  }
 
   std::cout << "Checks checked: " << checks_checked << '\n'
             << "Checks passed:  " << checks_passed << '\n';