World's first playable nesting Easter eggs in gaming?

There's a tradition to include hidden images or features in games, software, movies and other media. Such features is called Easter eggs referring to the Easter egg hunt.
One computer game can even contain another game. You can find entire Maniac Mansion in Day of the Tentacle for example. It's a common thing.
But in 2016 something special happened. I believe that the first nesting gaming Easter egg was made. But it seems like no one noticed it. It's time to correct this flaw.
I mean we have one game inside of another game inside of third game. And they are nested like Matryoshka dolls.
Astonishing, isn't it?
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Видео World's first playable nesting Easter eggs in gaming? канала ZX Spectrum Hotel