flame/examples/lib/stories/components/spawn_component_example.dart

import 'package:examples/commons/ember.dart';
import 'package:flame/components.dart';
import 'package:flame/events.dart';
import 'package:flame/experimental.dart';
import 'package:flame/extensions.dart';
import 'package:flame/game.dart';
import 'package:flame/math.dart';

class SpawnComponentExample extends FlameGame {
  static const String description =
      'Tap on the screen to start spawning Embers within different shapes.';

  SpawnComponentExample() : super(world: SpawnComponentWorld());
}

class SpawnComponentWorld extends World with TapCallbacks {
  @override
  void onTapDown(TapDownEvent info) {
    final shapeType = Shapes.values.random();

    final position = info.localPosition;
    final shape = switch (shapeType) {
      Shapes.rectangle => Rectangle.fromCenter(
        center: position,
        size: Vector2.all(200),
      ),
      Shapes.circle => Circle(position, 150),
      Shapes.polygon => Polygon(
        [
          Vector2(-1.0, 0.0),
          Vector2(-0.8, 0.6),
          Vector2(0.0, 1.0),
          Vector2(0.6, 0.9),
          Vector2(1.0, 0.0),
          Vector2(0.3, -0.2),
          Vector2(0.0, -1.0),
          Vector2(-0.8, -0.5),
        ].map((vertex) {
          return vertex
            ..scale(200)
            ..add(position);
        }).toList(),
      ),
    };

    add(
      SpawnComponent(
        factory: (_) => Ember(),
        period: 0.5,
        area: shape,
        within: randomFallback.nextBool(),
      ),
    );
  }
}

enum Shapes {
  rectangle,
  circle,
  polygon,
}