Impossible packs used to be impossible. Now they're a walk in the park for top players. People consistently put out packs much harder than the official impossible packs, so I added two new difficulties: Solar and Black Hole.
Solar difficulty should be beatable by any of the top players with lots of dedication, whereas Black Hole is reserved for the packs so hard that I would never have a chance. I added two new Steam achievements unlocked by beating each of these difficulties.