The game opens with D-9341 waking up and being pulled from his cell to begin testing. You play as D-9341, one of many Class-D test subjects used by the SCP Foundation, an organization dedicated to containing and safe-guarding anomalous creatures and artifacts from the rest of the world. This also encouraged Regalis to pursue a career in game designing, and ultimately lead to him founding Undertow Games. The positive feedback of it motivated Regalis to further expand the game over the years from what he calls ' a simple jumpscarefest revolving around SCP-173 to something I'd call a full blown game.' by the time v1.0 was released. SCP - Containment Breach v 0.1 was released on April 15th, 2012, and like SCP-087-B, Regalis was surprised by the overwhelming positivity and popularity the game had received. This promotion allowed the game to garner a lot of attention in the weeks leading towards its initial release. He also created short YouTube videos demonstrating various aspects of the game. When SCP - Containment Breach got closer to release, Regalis began circulating information about it through 4chan (specifically the '/x/' image board) and Reddit, similarly to how he promoted SCP-087-B. He would often use his friends as playtesters for the indev versions of it in order to provide feedback on what elements worked and did not work. To counter this, Regalis implemented the blinking mechanic. This choice lead to a design challenge in which SCP-173 was too easy to pass by when encountered. SCP-173 was chosen to be the primary threat and focus of the game as Regalis considered it one of his favorite SCPs. Like SCP-087-B, Regalis choose to use the Blitz3D engine for SCP - Containment Breach as he was already familiar with the program, meaning he would be able to easily create and troubleshoot the game. Development on what would later become SCP - Containment Breach began around March 2012.

The game received much more praise and attention than Regalis had expected, resulting in many people suggesting that he should try creating another SCP-based game with more content to it. This eventually lead to the creation and release of SCP-087-B on January 30th, 2012. The game became a viral success, catching the attention of Regalis, who became inspired to create a more varied version of the game which deviated from SCP-087's original article. On January 19th, 2012, a YouTube user who goes by the name of 'Haversine' released a short clip of an experimental game they are working on called SCP-087, based upon the SCP of the same name. The game (which I named SCP-087-B) got way more popular than I could have even imagined, and people started suggesting that I should make a more extensive game of some other SCP, with gameplay that isn't just walking down stairs.

Scp containment breach controls