diff --git a/assign3.md b/assign3.md
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+++ b/assign3.md
@@ -207,6 +207,8 @@ to:
 - update the score
 - ensure that the board's layout / draw methods are called by calling `board.setNeedsDisplay()`
 
+**Do not add any externally accessed methods or properties in your custom view.**
+
 ## Task 4: Animation
 Implement tile animation entirely in your `BoardView` class:
 - animate new tiles but starting them w/ opacity of 0 and animating to opacity