small fix

lib/main.dart

@@ -70,32 +70,35 @@ class _MyHomePageState extends State<MyHomePage> {
     _grid = List.generate(widget.gridSize, (_) => List.generate(widget.gridSize, (_) => Random().nextInt(5)));
   }
 
+  @override
   Widget build(BuildContext context) {
     return Scaffold(
       appBar: AppBar(
         title: Text('Candy Crush'),
       ),
       body: Center(
-        child: GridView.builder(
-          shrinkWrap: true,
-          gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
-            crossAxisCount: widget.gridSize,
-          ),
-          itemCount: widget.gridSize * widget.gridSize,
-          itemBuilder: (BuildContext context, int index) {
-            int row = index ~/ widget.gridSize;
-            int col = index % widget.gridSize;
-            return GestureDetector(
-              onTap: () => _onTileTap(row, col),
-              child: Container(
-                margin: EdgeInsets.all(2),
-                decoration: BoxDecoration(
-                  color: _getColor(_grid[row][col]),
-                  borderRadius: BorderRadius.circular(8),
+        child: Expanded(
+          child: GridView.builder(
+            shrinkWrap: true,
+            gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
+              crossAxisCount: widget.gridSize,
+            ),
+            itemCount: widget.gridSize * widget.gridSize,
+            itemBuilder: (BuildContext context, int index) {
+              int row = index ~/ widget.gridSize;
+              int col = index % widget.gridSize;
+              return GestureDetector(
+                onTap: () => _onTileTap(row, col),
+                child: Container(
+                  margin: EdgeInsets.all(2),
+                  decoration: BoxDecoration(
+                    color: _getColor(_grid[row][col]),
+                    borderRadius: BorderRadius.circular(8),
+                  ),
                 ),
-              ),
-            );
-          },
+              );
+            },
+          ),
         ),
       ),
     );