diff --git a/lib/bowling_game.dart b/lib/bowling_game.dart
index a900cb8..b4983c5 100644
--- a/lib/bowling_game.dart
+++ b/lib/bowling_game.dart
@@ -1,7 +1,11 @@
 class BowlingGame {
-  void roll(int pins) {}
+  int _score = 0;
+
+  void roll(int pins) {
+    _score += pins;
+  }
 
   int score() {
-    return 0;
+    return _score;
   }
 }