flame/doc/examples/parallax/lib/main_game.dart

import 'package:flame/components.dart';
import 'package:flame/flame.dart';
import 'package:flame/game.dart';
import 'package:flame/parallax.dart';
import 'package:flame/extensions.dart';
import 'package:flutter/material.dart';

/// This examples serves to test the Parallax feature outside of the
/// Flame Component System (FCS), use the other files in this folder
/// for examples on how to use parallax with FCS
/// FCS is only used when you extend BaseGame, not Game,
/// like we do in this example.
void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Flame.device.fullScreen();
  runApp(
    GameWidget(
      game: MyGame(),
    ),
  );
}

class MyGame extends Game {
  late Parallax parallax;

  @override
  Future<void> onLoad() async {
    parallax = await loadParallax(
      [
        'bg.png',
        'mountain-far.png',
        'mountains.png',
        'trees.png',
        'foreground-trees.png',
      ],
      size,
      baseVelocity: Vector2(20, 0),
      velocityMultiplierDelta: Vector2(1.8, 1.0),
    );
  }

  @override
  void update(double dt) {
    parallax.update(dt);
  }

  @override
  void render(Canvas canvas) {
    parallax.render(canvas);
  }
}