Use Dart 2 camel case constants (#15360)
diff --git a/examples/layers/widgets/spinning_square.dart b/examples/layers/widgets/spinning_square.dart
index be59f1c..81312d6 100644
--- a/examples/layers/widgets/spinning_square.dart
+++ b/examples/layers/widgets/spinning_square.dart
@@ -17,7 +17,7 @@
super.initState();
// We use 3600 milliseconds instead of 1800 milliseconds because 0.0 -> 1.0
// represents an entire turn of the square whereas in the other examples
- // we used 0.0 -> math.PI, which is only half a turn.
+ // we used 0.0 -> math.pi, which is only half a turn.
_animation = new AnimationController(
duration: const Duration(milliseconds: 3600),
vsync: this,
