diff --git a/app/react-components/devtools.jsx b/app/react-components/devtools.jsx
index 01e9ccf..4ae0816 100644
--- a/app/react-components/devtools.jsx
+++ b/app/react-components/devtools.jsx
@@ -74,6 +74,12 @@ export default function Devtools({
             return;
           }
           const {left, top} = offsetRef.current.getBoundingClientRect();
+          if (
+            event.clientX - left >= w
+            || event.clientY - top >= h
+          ) {
+            return;
+          }
           const x = Math.floor((event.clientX - left) / tileSize.x);
           const y = Math.floor((event.clientY - top) / tileSize.y);
           setMoveStart({x, y});