Want to animate a sprite to move to an arbitrary point in flutter? Adding a key like so, seems to be the answer to API question, the key tells the flutter which AnimatedPositioned widget is which between updates so It can know where each begins its journey, without it each is new on each update and the old one is gone so there is no beginnig position to use:
duration: Duration(milliseconds: 900),
style: TextStyle(color: Colors.black, fontSize: roomLength),
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