On the morning of Jan. 9, Josh Millard sent a tweet to his 1,059 followers:

“You ever played Super Mario Bros, right? Please draw a map of world 1-1 from memory, best as you can. No cheating.”

The result of this challenge was Mapstalgia, a quickly growing Tumblr blog that showcases video-game world maps drawn from memory.

“My main interest in the project is in seeing how people remember and how the holes in memory manifest in these drawings,” Millard told the Daily Dot.

Inspired by a discussion with a coworker at MetaFilter, the social news site where Millard works as an administrator, he began thinking about how video games take place in imaginary worlds. Yet these worlds still become ingrained in players’ heads. He wondered how similar players’ memories of these shared worlds could be.

“The worlds may be fictional but our mental maps of them are as real as anything else we remember. And they’re shared experiences: my experience in Super Mario Bros. was a lot like yours, and even if we never played it together, it’s a space we have in common,” he wrote on Mapstalgia’s inaugural post.

Since then, Mapstalgia has attracted 942 followers and write-ups on video game sites as big as Kotaku. He’s got more than 100 map submissions waiting in a queue, and more than 150 live on the blog, including his own attempt at Super Mario Bros 1-1.

“I love that some of these look like not just maps but art pieces, and others could be reliably used to navigate some very complicated game worlds,” he told us. “Some people have amazing memories.”

In the future, Millard would like to turn the map collection into a physical book. However, he said that until he figures out to credit the cartographers more explicitly, it’s not in the cards.

“It’s something I’d love to own, certainly, and I think a lot of other folks would too,” he said. “[A] very exciting idea but one to think about a little farther down the road.”

We’ve collected a few of these maps below: