I wrote
DanmakU for Unity 5.2, but I have had zero interest in reviving it or updating it. Feel free to do with it what you want. There has been some recent interest in reviving it by several people, if you guys want to get together and recreate it, be my guest. The end goal was to create a Danmakufu like under-engine that provides highly granular control over individual elements, but also build on top of that a powerful declarative domain specific language for creating bullet patterns:
// Serialize MonoBehaviour fields for easy Editor configuration
[SerializeField]
DanmakuCircle circle;
[SerializeField]
DanmakuLine line;
[SerializeField]
DanmakuPrefab bullet;
void Awake() {
// Composable pattern structure
Fire(circle.Of(line).Of(bullet))
// Parameterize the nature of how it should be fired
.Towards(Player)
// Further configure how it should be fired
.Every(5.Seconds()).Until(spellcardOver);
}
There's definitely several danmaku/bullet hell packages on the Unity Asset Store, but they're not exactly free.
I am certainly interested in following the development of the fangame. Can't say I can help out with my current schedule.