2
2

with SingleTickerProviderStateMixin {

3
3

late AnimationController _controller;

+
              late Animation<Alignment> _animation;

4
5

Alignment _dragAlignment = Alignment.center;

Next, update _dragAlignment when the AnimationController produces a
value:

lib/{step2.dart (initState) → step3.dart (initState)}

@@ -3,4 +3,9 @@

3
3

super.initState();

4
4

_controller =

5
5

AnimationController(vsync: this, duration: const Duration(seconds: 1));

+
              _controller.addListener(() {

+
                setState(() {