Deadlock
Deadlock is a Source 2 engine game by Valve Software. The game had previously been known as Citadel (which can still be seen in the game directory: https://steamdb.info/patchnotes/14645631/) and later Neon Prime but the current title Deadlock was revealed by early play-testers on 16th May 2024. https://playdeadlock.com/ and https://x.com/playdeadlock were both registered in April 2024 though neither were reported until 16th May 2024. The name Neon Prime had been revealed in a trademark application in October 2022 https://tsdr.uspto.gov/#caseNumber=97625459&caseSearchType=US_APPLICATION&caseType=DEFAULT&searchType=statusSearch but the application was opposed in November 2023. During this time there were various rumours about the game, including that it was set in an existing universe created by Valve.
On 16th May 2024 it was revealed that Deadlock was undergoing private play-testing of an "Early Development Build", apparently by hundreds of people, though it was unclear when the play-testing had begun. Reportedly the play-testers were not subject to NDAs. A number of screenshots and videos were released and in the following days including a screenshot and video of the earlier iteration Neon Prime from December 2023: this screenshot and video showed a game with a science fiction theme though this was changed significantly for the current iteration, although the gameplay appeared similar. A number of videos were linked from https://project8.dev/ which is rumoured to be the play-testers forum. The name project8 is a codename for the game with the early playtest's executable being called project8.exe. Closed testing continued through May and into June with players being able to invite people by email and then in June being able to invite Steam friends. On August 9th 2024 the forum URL was changed from project8.dev to playdeadlock.com. On August 12th 2024, TheVerge published an article on the new game in spite of the game asking players not to share anything. The same day, the article's author was banned from matchmaking (Hollister, https://www.theverge.com/2024/8/12/24219016/valve-deadlock-hands-on-secret-new-game).
On August 21st 2024 a number of tags were added to the game's Steam profile (https://x.com/gabefollower/status/1826340710230184184) and on August 24th 2024, the embargo was lifted (https://knockout.chat/thread/61913/34#post-2327624) and the game's Steam page was made public (https://knockout.chat/thread/61913/34#post-2327628).
