how did google made reverse domain of "http://com.google" for April fools day 2015?

you can find a reverse google at https://com.google/ my question is how did they do that!?

a reverse domain? a dot google! as i know there is no domain name for dot google sites! i searched it in who.is for it and they also think there is no domain such that! you can see it here: http://ift.tt/1F1Gvs4

so how did they reverse the google.com to com.google!? any one have an answer please?