diff --git a/Parameters_September21.md b/Parameters_September21.md
index 9b3d44a..e62ec7c 100644
--- a/Parameters_September21.md
+++ b/Parameters_September21.md
@@ -163,7 +163,7 @@ updated gradually.
 
 ```
 
-### 29 September 21 -  ###
+### 29 September 21 - 3 light sources in a Penrose unilluminable room ###
 
 **Program:** `particle_billiard.c`