diff --git a/engine/geometry/cute_c2_ext.h b/engine/geometry/cute_c2_ext.h
index cda2db5..8550600 100644
--- a/engine/geometry/cute_c2_ext.h
+++ b/engine/geometry/cute_c2_ext.h
@@ -1,4 +1,14 @@
 #include "cute_c2.h"
+/**
+ * Current version of C2 has no calculation for contact point and normal
+ * for TOI calculation.
+ * However, a discussion by Tyler Glaiel:
+ * https://github.com/RandyGaul/cute_headers/issues/155
+ *
+ * resulted in specfic functions to do so.
+ * These are shamelessly copied over with almost no modification.
+ * Thank you, Tyler!
+ */
 double PointToSegmentTOI(c2v p, c2v v, c2v a, c2v b);
 
 double PointToCircleTOI(c2v p, c2v v, c2v circ_p, double r);