GLOBAL – Since 1998, an anonymous French citizen who identifies himself as an Unidentified Free Artist (UFA) and goes by the name Invader has developed a public art project that’s reached around the world…and beyond. The project, Space Invaders, “liberates art from its usual alienators”—museums and other institutions—and introduces pixelated, video-game-like ceramic tile invader figures into our physical world.

Invader considers his project contemporary art, graffiti, street art, and more, as well as “the most addictive game I’ve ever played.” When he invades a new city, he installs from 20 to 50 mosaic figures of varying colors and designs, each with its own title. (The invaders even rack up imaginary game points each time they arrive in a new location.) As of this writing, 3,339 invaders have populated 66 cities.

And in 2015, the project actually invaded space: an invader titled SPACE2 was installed on the International Space Station. Explorers in the other direction can also sample Invader’s work: with scuba gear, they can discover two (authorized) invaders attached to Jason deCaires Taylor’s sculptures deep in Mexico’s Cancun Bay.