Serious Sam HD: The First Encounter is a remake of Serious Sam: The First Encounter. The entire game starting from the story over the levels with their secrets, monsters, weapons and power-ups remain entirely the same as in the original game but everything has been graphically enhanced through the use of the Serious Engine 3.
The player still takes on the role of Serious "Sam" Stone in a traditional first-person-shooter-style. Sam is send back in time to prevent the destruction of mankind in the 21st Century by an alien known as Mental. But ancient Egypt isn't as we were told. Instead hundreds and hundreds of Mental's minions including the now famous Beheaded Bomber, several kinds of Bio-Mechanoids and Lava Golems lurk around the pyramids and ancient cities or get teleported there once Sam enters a certain area or triggers a script in the linear levels. To deal with these enemies, Sam has ten weapons at his disposable ranging from his trusty revolvers with unlimited ammo over a chain-gun to the all-powerful "SeriousBomb?"-Cannon.
As opposed to the original game, Serious Sam HD: The First Encounter in it's original released version only features a coop-mode for up to 16 players both over LAN and WAN and no deathmatch modes, which was later implemented by a major update through Steam. The Xbox 360 version does not support offline multiplayer game modes.