Serious Sam: The First Encounter is a first-person shooter video game developed by Croteam and originally published by Gathering of Developers, first released on Microsoft Windows on 21 March 2001. It had been in development since 1996 and had videos showing its early gameplay in 2000. The First Encounter was originally developed by Croteam as a demonstrator for their engine, which was why some countries saw its initial release priced at less than half the price of other games in the genre. This game was followed by a sequel, Serious Sam: The Second Encounter, released eleven months later.