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I actually found this by looking for any good-looking mods to play. After looking through the comments I thought "Wait, Notch tweeted it??".
The usual praises about the narrator.
Is there a way to add custom levels to this game?
That's a shader error. It's in the steam help section. A temp fix is lowering the Direct X level to 8.1. However, you also lose HDR and other fancy stuff.