diff --git a/readme.md b/readme.md
index 999714f..c47d21a 100644
--- a/readme.md
+++ b/readme.md
@@ -50,6 +50,7 @@ if (src.match(/^(file|https)?:\/\/|^\/\//)) {
 ## to do
 
 * test new room ID handling!!!
+* don't reuse wall tiles
 * add 'clear'/'upload' buttons for game data
 * select all on clicking game data entry field
 * allow user to save output as image, or tweet it :)