The page shows the game running in an in-browser emulation of the DEC PDP-1 (in html5/JavaScript). The project was an entry to RetroChallenge 2016/10 [1]. A writeup/blog is available at http://www.masswerk.at/rc2016/10/

In a nutshell, the program brings Computer Space, the very first coin-op. arcade video game (by Nolan Bushnell and Ted Dabney, Syzygy Engineering / Nutting Associates, 1971) to the machine, which's showcase application "Spacewar!" (1961/62) had inspired it in the first place. Notably, Computer Space was not a program, but an electronic device in 74xx TTL logic.

[1] RetroChallenge is "a loosely disorganised gathering of RetroComputing enthusiasts who collectively do stuff with old computers for a month." http://retrochallenge.net