diff --git a/Makefile.mak b/Makefile.mak
index 97c7f400..2fd6dee7 100644
--- a/Makefile.mak
+++ b/Makefile.mak
@@ -73,7 +73,7 @@ bin\th04\op.exe: bin\th04\op.obj th04\op_02.c
 $**
 |
 
-bin\th05\main.exe: bin\th05\main.obj th05\main_01.c
+bin\th05\main.exe: bin\th05\main.obj th05\main_01.cpp
 	$(CC) $(CFLAGS) -ml -3 -DGAME=5 -nbin\th05\ -eMAIN.EXE @&&|
 $**
 |
diff --git a/th04/shared.h b/th04/shared.h
deleted file mode 100644
index 08ddebef..00000000
--- a/th04/shared.h
+++ /dev/null
@@ -1,14 +0,0 @@
-/* ReC98
- * -----
- * Types shared between TH04 and TH05
- */
-
-/// Score
-/// -----
-extern unsigned long score_delta;
-
-void pascal near score_update_and_render(void);
-
-// Adds the entire score delta at once to the current score.
-void pascal score_delta_commit(void);
-/// -----
diff --git a/th04/shared.hpp b/th04/shared.hpp
new file mode 100644
index 00000000..2794f58e
--- /dev/null
+++ b/th04/shared.hpp
@@ -0,0 +1,53 @@
+/* ReC98
+ * -----
+ * Types shared between TH04 and TH05
+ */
+
+/// Math
+/// ----
+class Subpixel {
+private:
+	int v;
+
+public:
+	Subpixel() {}
+	Subpixel(float screen_v) { *this = screen_v; }
+
+	Subpixel& operator =(float screen_v) {
+		v = static_cast<int>(screen_v * 16.0f);
+		return *this;
+	}
+};
+
+struct SPPoint {
+	Subpixel x, y;
+
+	void set(float screen_x, float screen_y) {
+		x = screen_x;
+		y = screen_y;
+	}
+};
+
+typedef struct {
+	SPPoint cur;
+	SPPoint prev;
+	SPPoint velocity;
+
+	void init(float screen_x, float screen_y) {
+		cur.x = screen_x;
+		prev.x = screen_x;
+		cur.y = screen_y;
+		prev.y = screen_y;
+	}
+} motion_t;
+/// ----
+
+/// Score
+/// -----
+extern unsigned long score_delta;
+
+void pascal near score_update_and_render(void);
+
+// Adds the entire score delta at once to the current score.
+void pascal score_delta_commit(void);
+/// -----
diff --git a/th05/main_01.c b/th05/main_01.cpp
similarity index 84%
rename from th05/main_01.c
rename to th05/main_01.cpp
index 93d5b48b..eed86542 100644
--- a/th05/main_01.c
+++ b/th05/main_01.cpp
@@ -3,7 +3,8 @@
  * Code segment #1 of TH05's MAIN.EXE
  */
 
-#include "th05/th05.h"
+extern "C" {
+#include "th05/th05.hpp"
 
 // Adds the entire score delta at once to the current score.
 void pascal score_delta_commit(void)
@@ -12,3 +13,5 @@ void pascal score_delta_commit(void)
 		score_update_and_render();
 	}
 }
+
+}
diff --git a/th05/th05.h b/th05/th05.hpp
similarity index 59%
rename from th05/th05.h
rename to th05/th05.hpp
index 960fbd61..ff8c1cbc 100644
--- a/th05/th05.h
+++ b/th05/th05.hpp
@@ -4,4 +4,5 @@
  */
 
 #include "ReC98.h"
-#include "th04/shared.h"
+#include "th04/shared.hpp"
+/// ------