A new mod for Half-Life 2 has just come out which essentially reverses the entire game, making the experience pretty surreal. The title has been out since 2004 and although a third game in the series is likely not going to happen, the 18 years that have elapsed since the second installment was released means that many fans probably know every aspect of the sequel in great detail. Given this, players have likely formed habits forged over many years, but things are about to get topsy-turvy.