src/main.dart

@@ -119,7 +119,7 @@ class Tile extends StatelessWidget {
 
     @override
     Widget build(BuildContext context) {
-        return Container(
+        return AnimatedContainer(
             child: Center(
                 child: Text(
                     letter.toUpperCase(),
@@ -130,6 +130,7 @@ class Tile extends StatelessWidget {
                 border: Border.all(color: Colors.grey.shade300),
                 color: tutTileColor(hitType),
             ),
+            duration: Duration(milliseconds: 300),
             height: 60,
             width: 60,
         );