diff --git a/TODO.md b/TODO.md
new file mode 100644
index 0000000..2b9fa56
--- /dev/null
+++ b/TODO.md
@@ -0,0 +1,6 @@
+#TODO:
+
+## refactoring
+
+- [ ] fp.gear.z -> fp.gear.num_teeth
+- [ ] fp.teeth  -> fp.gear.num_teeth
\ No newline at end of file