diff --git a/.gitmodules b/.gitmodules
index d95c6c3..456be71 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -5,6 +5,6 @@
 [submodule "external/glm"]
 	path = external/glm
 	url = https://github.com/g-truc/glm.git
-[submodule "bullet3"]
-	path = bullet3
+[submodule "external/bullet3"]
+	path = external/bullet3
 	url = https://github.com/bulletphysics/bullet3.git
diff --git a/external/SDL b/external/SDL
new file mode 160000
index 0000000..6051535
--- /dev/null
+++ b/external/SDL
@@ -0,0 +1 @@
+Subproject commit 60515350ae2c30334b6f4c55480eb247cd879333
diff --git a/external/bullet3 b/external/bullet3
new file mode 160000
index 0000000..d1a4256
--- /dev/null
+++ b/external/bullet3
@@ -0,0 +1 @@
+Subproject commit d1a4256b3a019117f2bb6cb8c63d6367aaf512e2
diff --git a/external/glm b/external/glm
new file mode 160000
index 0000000..2d4c4b4
--- /dev/null
+++ b/external/glm
@@ -0,0 +1 @@
+Subproject commit 2d4c4b4dd31fde06cfffad7915c2b3006402322f