One of the best video games ever made was released 15 years ago today as a free extra

"Here Come The Test Results: You Are A Horrible Person. We Weren’t Even Testing For That."

How often do video games come along that essentially change the medium as we know it? Let us answer that one for you: Not very often. So when we say that Portal completely upended gaming, we mean it. Pairing incredibly inventive gameplay mechanics with brain-melting puzzles and - the-rarest-of-rares - an actually funny script, Portal came out of nowhere to blow everyone away. Released on 10 October 2007, it has joined other famous Valve game franchises - Half-Life, Team Fortress, Left 4 Dead - which never got beyond one sequel, leaving fans in a constant state of anticipation for a decade and a half. Unlike those other franchises, this one essentially began its life as a freebie add-on. The game began properly in 2005, when Valve president Gabe Newell saw footage from an independent game titled Narbacular Drop, and immediately hired the entire team. That game involved a princess trying to escape from a dungeon... using a portal gun. A little over two years later, from a team no bigger than 10 people, the central puzzle/platform hybrid of Narbacular Drop had changed into something very different. The Orange Box launched on 10 October 2007, and it included Half-Life 2, Half-Life 2: Episode One, Half-Life 2: Episode Two, Team Fortress 2... and Portal. Pretty much everyone purchased the collection to check out the latest entry in the incredible Half-Life franchise, and ended up becoming fully lost in this new world of test centres, armed sentries, and blue and orange blobs of space distortion. You play as Chell, who wakes up in a stark, clinical space, and are given a portal gun to use to get around different test chambers. Along the way, an artificial intelligence named GLaDOS (Genetic Lifeform and Disk Operating System) narrates your progress, but may actually have more investment in your success than it is initially letting on... Once the games collection was released, it didn't take long for critics and gamers to realise how special Portal was. It was initially flooded with Game Of The Year awards, but in the 15 years since, the impact is still being felt. Time Magazine ranked it among the 100 best games of all time. Wired titled it one of the most influential games of the 21st century. GamesRadar named it the best game ever made. The list goes on and on and on. We would eventually get the also brilliant Portal 2 in 2011, and Hollywood has been toying with an adaptation of the story since 2013, but nothing has come of it as of yet. At the time of writing, Portal is available to play on PlayStation, Xbox, PC, Mac, Mobile and Switch.