To be completely run in a console app as well.

### Separation of interest so that it can be completely executed in a console app as well.


**Console application execution**

```
$ dart run bin/main.dart
```

lib/src/stage_state.dartの `import 'package:flame/components.dart'` の依存（Dart library 'dart:ui'）により、コンソールから実行できなくなっているので実行できるように、依存をなくす。

こちら使用。
https://pub.dev/packages/dart_console