moving_hole/lib/main.dart

import 'package:flutter/material.dart';
import 'package:flutter/scheduler.dart';
import 'dart:async';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(home: Scaffold(body: App()));
  }
}

class App extends StatefulWidget {
  @override
  AppState createState() => AppState();
}

class AppState extends State<App> with SingleTickerProviderStateMixin {
  AnimationController _controller;

  @override
  void initState() {
    super.initState();
    _controller = AnimationController(
      duration: Duration(seconds: 9),
      vsync: this,
    );
  }

  @override
  void dispose() {
    _controller?.dispose();
    super.dispose();
  }

  Future _startAnim() async {
    try {
      await _controller.forward().orCancel;
      // await _controller.reverse().orCancel;
    } on TickerCanceled {
      print('welp we fucked');
    }
  }

  @override
  Widget build(BuildContext context) {
    return Material(
        child: GestureDetector(
      onTap: () {
        _startAnim();
      },
      child: Stack(
        fit: StackFit.expand,
        children: [
          Image.network(
            'https://wallpaperplay.com/walls/full/e/5/3/13586.jpg',
            fit: BoxFit.cover,
          ),
          ColorFiltered(
            colorFilter: ColorFilter.mode(Colors.black.withOpacity(0.8),
                BlendMode.srcOut), // This one will create the magic
            child: Stack(
              fit: StackFit.expand,
              children: [
                Container(
                  decoration: BoxDecoration(
                      color: Colors.black,
                      backgroundBlendMode: BlendMode
                          .dstOut), // This one will handle background + difference out
                ),
                MovingHole(controller: _controller)
              ],
            ),
          ),
        ],
      ),
    ));
  }
}

class MovingHole extends StatelessWidget {
  MovingHole({Key key, this.controller})
      : width = TweenSequence(
          <TweenSequenceItem<double>>[
            TweenSequenceItem<double>(
              tween: Tween<double>(begin: 100, end: 150)
                  .chain(CurveTween(curve: Curves.ease)),
              weight: 33.0,
            ),
            TweenSequenceItem<double>(
              tween: Tween<double>(begin: 150, end: 200),
              weight: 33.0,
            ),
            TweenSequenceItem<double>(
              tween: Tween<double>(begin: 200, end: 300)
                  .chain(CurveTween(curve: Curves.ease)),
              weight: 33.0,
            ),
          ],
        ).animate(CurvedAnimation(
            parent: controller, curve: Interval(0.0, 1, curve: Curves.linear))),
        height = TweenSequence(
          <TweenSequenceItem<double>>[
            TweenSequenceItem<double>(
              tween: Tween<double>(begin: 100, end: 150)
                  .chain(CurveTween(curve: Curves.ease)),
              weight: 40.0,
            ),
            TweenSequenceItem<double>(
              tween: Tween<double>(begin: 150, end: 200),
              weight: 20.0,
            ),
            TweenSequenceItem<double>(
              tween: Tween<double>(begin: 200, end: 300)
                  .chain(CurveTween(curve: Curves.ease)),
              weight: 40.0,
            ),
          ],
        ).animate(CurvedAnimation(
            parent: controller,
            curve: Interval(0.0, 1, curve: Curves.fastOutSlowIn))),
        radius = BorderRadiusTween(
                begin: BorderRadius.circular(0.0),
                end: BorderRadius.circular(100.0))
            .animate(CurvedAnimation(
                parent: controller,
                curve: Interval(
                  0.0,
                  1,
                  curve: Curves.ease,
                ))),
        alignment = AlignmentTween(
                begin: Alignment.bottomCenter, end: Alignment.topCenter)
            .animate(CurvedAnimation(
                parent: controller,
                curve: Interval(0.0, 1, curve: Curves.ease))),
        super(key: key);

  Animation<double> controller;
  Animation<double> width;
  Animation<double> height;
  Animation<BorderRadius> radius;
  Animation<Alignment> alignment;

  Widget build(BuildContext context) {
    return AnimatedBuilder(
        animation: controller,
        builder: (BuildContext context, Widget child) {
          return Container(
              alignment: alignment.value,
              child: Container(
                width: width.value,
                height: height.value,
                decoration: BoxDecoration(
                    color: Colors.red, borderRadius: radius.value),
              ));
        });
  }
}