diff --git a/README.md b/README.md
index dd2d284..370647d 100644
--- a/README.md
+++ b/README.md
@@ -12,3 +12,5 @@
 - u: undo
 - f: save current state to "lastBoard.txt"
 - c: solve the puzzle
+- -: zoom out
+- =: zoom in