What's _UniqueID?

[Luxiere]

In the project you created a Material Property Block and SetFloat("_UniqueID", Random.Value) to it. Is the _UniqueID the instance unique ID? Why do you need to set this value?

[keijiro]

// This property block is used only for avoiding an instancing bug.

As noted in the comment, it's a workaround for an instancing bug inside Unity. I can't remember what it was... I think it has been fixed in the current version.