The Serious Sam series is back for its third main (though sixth overall) outing. Running on the new Serious Engine 3.5, Serious Sam 3: BFE serves as a prequel to the original First Encounter; a fact referenced in the games title, BFE standing for Before First Encounter. Set in the 22nd century, the plot revolves around a device known as the "Time-Lock;" a discovery made beneath the ruins of ancient Egypt, found to belong to an even older yet technologically advanced civilization known as the Sirians. However this discovery catches the attention of a dangerous cosmic entity known as Notorious Mental, who assaults Egypt and seizes the Time-Lock as his own, abusing its powers to create a horde of cloned beasts borrowed from various points and places in the universes history to unleash upon the Earth. Various attempts to retake Egypt and reach the Time-Lock have failed, until a new task force is sent in with "Serious" Sam Stone on board, and despite being separated from his team - Sam plows forward with all the weaponry he can find.
Like the previous entries in the series, the game is a simple, arcade-style shooter that throws back many elements to the early days of the genre with games such as Wolfenstein 3D, Doom and Duke Nukem 3D. When the player chooses a difficulty, the game applies a score modifier based on difficulty and also applies score variables on time, saves made, and enemy kills - tallied at the end of each level. SS3 also continues the trend of having the player fight large amounts of enemies with any weapon at their disposal. The weapons themselves range from conventional tools such as a pistol, shotgun, and assault rifle while also giving players some less conventional weapons such as a portable cannon, laser-rifle and a new entry to the series - the mutilator.
Outside of the single player mode, there are various multiplayer options that can be played online with up to 16 players and split-screen with up to 4 players. These modes include cooperative campaigns, survival missions, and a "beast hunt" mode as well as traditional deathmatch and team deathmatch options and a new "my burden" mode.