https://www.pcgamer.com/bungie-files-mysterious-trademark-for-matter/

A trademark filing in the EU has revealed an unannounced Bungie project: “Matter.” Filed by a UK law firm representing the American company, Matter is filed under the classifications for “video game software” and “electronic games services provided by means of the internet or other communication network.” 

In other words: It’s a videogame. Will it be a PC Game? Hopefully. It’s probably worth noting that the second classification can also indicate a service which allows the downloading or playing of games, as unlikely as Bungie launching its own Steam competitor or eSports tournament service seems.