Update README.md

Author: ss892714028

README.md

@@ -1,10 +1,12 @@
 ## Maze PathFinder Visualization implemented in Python
 ### How to use
 * The first two left clicks on the board initialize start and end node
-* Press space bar and see the algorithm go!
+* Click or click and drag to create obstacles
+* Press space bar and see the algorithm takes off!
 ### Symbols
 #### @: Start and end node
-#### #: Visited node
+#### #: Obstacles
+#### .: Visited node
 ##### +: Path
 
 ### Breadth First Search