At the dawn of the 21st century, mankind made an astounding discovery. Beneath the Egyptian civilization lies an undiscovered one. With scientific research, this discovery led humankind to the far reaches of the universe. Everything was going very well, but too well to last. In the year 2104 countless deadly monsters attacked the human civilization, spawned from a different dimension. The humans fought valiantly, but nothing seemed to stop the monsters from coming. Earth's forces were steadily defeated, planet by planet, from Alpha Centauri back to their own solar system. Because of his extreme bravery in battling the monsters, Sam "Serious" Stone became a legend. Sam is a living symbol of Earth's resistance against the advancing evil. But no matter how brave the human armies were, they were defeated, time after time. Attempts to defend the solar system fail, and Earth is now under a direct attack. Earth was about to be annihilated. World leaders must now turn to their last chance, the ancient artifact called the "Time Lock", a relic from a long-forgotten race, imbued with the power to teleport a single person back in time. The choice of whom to send was obvious. Sam was sent back in time to Egypt, where he would purge every last one of the Aliens plaguing the area.
All games in the Serious Sam series all feature fast, intense and frantic gameplay. They reflect the slogan of the series, "No cover, all man" very well with enemies that easily either burst down cover or run around it with ease.
The games feature lots of different weapons, like the shotgun, which is one of the middle class weapons in the game. In the first two games, Serious Sam: The First Encounter and Serious Sam: The Second Encounter, there are a total of twelve weapons collectable. In Serious Sam II, there are even more.
The number of enemies in each level can top fifty at a time, easily. The player must fight through non-stop, action-packed fun to complete each level. There is lots of variety in the enemies that the player must fight, leaving them always surprised by a new feature of the game. There are very few dull moments in the games, with the almost complete lack of cutscenes, and even those are skippable, and fast-paced gameplay.
The Serious Sam series all use the Serious Engine to run them. The Serious Engine started off as a very simple model, that could hold up to one thousand entities on a single CPU in 1995. After a lot of optimization, the number of enemies it could hold topped one million. It was very efficient.
After the first games release, there was a newer, more efficient engine created, named Serious Engine 2. It was capable of holding a lot more entities on the screen, and it was praised greatly by critics and gamers everywhere.
Then came Serious Engine 3, which was used by Croteam to remake the first two games they made. This spawned Serious Sam HD: The First Encounter, and Serious Sam HD: The Second Encounter. To put it simply, these were little more than graphically improved versions of the originals.
And finally, there was Serious Engine 3.5, which is the engine that Croteam used to make Serious Sam 3: BFE. It was very similiar to Serious Engine 3, hence being named Serious Engine 3.5, but it added many more features, weapons, enemies, and textures.
The Serious Sam games (In the exclusion of the Indie series), all came with a level editor. This was named the Serious Editor. It went along with the engines, Serious Editor 1 went with the Serious Engine 1, Serious Editor 2 with Serious Engine 2, and so on and so forth. These Serious Editors allowed the player to create customized maps for them or others to play on, and even edit existing levels. Along with the Serious Editor, there is also the Serious Modeler. This allows players to customize models for those who want to create their own enemies or friends or entities, or, well, anything that requires a model to exist.
There have been lots and lots of custom levels and level packs created so far, a list of which can be found on the Seriously! forums.
The Serious Sam series consists of eight games, and two downloadable contents. Serious Sam was originally released for the PC running Windows, but because of its popularity, it has also been released to the Xbox, PlayStation 2, Gameboy Advance, and Xbox 360. Serious Sam: The First Encounter and Serious Sam: The Second Encounter were packed into one package, named Serious Sam: Gold. Serious Sam: Gold included both games previously mentioned, and an exceptionally good fanmade level pack. A full list of the games created is:
- Serious Sam: The First Encounter
- Serious Sam: The Second Encounter
- Serious Sam II
- Serious Sam: Double D
- Serious Sam: The Random Encounter
- Serious Sam HD: The First Encounter
- Serious Sam HD: The Second Encounter
- Serious Sam HD: The Legend of the Beast
- Serious Sam 3: BFE
- Serious Sam 3: The Jewel of the Nile
The game is said to be a first-person shooter, but it can also be categorized as a third-person shooter, as player can press the H key (default) to switch to third-person during gameplay.
The game was first conceived of in 1997, four years before its release.