diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000000000000000000000000000000000000..7a1d2295c4bbf18b02c188312d250ff3f3e89c5f
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,4 @@
+build/cluster/*
+build/sphere/*
+build/trapping/*
+
diff --git a/src/cluster/.gitkeep b/src/cluster/.gitkeep
new file mode 100644
index 0000000000000000000000000000000000000000..e69de29bb2d1d6434b8b29ae775ad8c2e48c5391
diff --git a/src/sphere/.gitkeep b/src/sphere/.gitkeep
new file mode 100644
index 0000000000000000000000000000000000000000..e69de29bb2d1d6434b8b29ae775ad8c2e48c5391
diff --git a/src/trapping/.gitkeep b/src/trapping/.gitkeep
new file mode 100644
index 0000000000000000000000000000000000000000..e69de29bb2d1d6434b8b29ae775ad8c2e48c5391