Serious Sam 2's gameplay consists almost entirely of the player attempting to defeat dozens of enemies at a time, and thus is relatively simple. The game's story establishes the reasons and methods for how the player travels from chapter to chapter. This is a significant change from the previous games in the series in which the story existed merely to transport the player from place to place in order to kill as many enemies as possible in the process, with the plot consisting merely of messages that the player could disregard without consequence. Serious Sam 2 features the story more prominently, but still maintains the focus on killing as many enemies as possible.[7][8] The story is developed through the use of cut scenes, which are interspersed throughout the game, especially at the beginning and end of each Planet.[9]
The player begins with a certain number of lives that represent the number of times the player is allowed to lose all of his health (and then re-spawn immediately from the player's last saved checkpoint). More complicated gameplay mechanics that are often found in other games (such as jumping puzzles) are rare, and when encountered they are fairly simple, usually requiring the player to locate keys/objects in order to unlock doors or advance to the next level. Player-controlled vehicles (such as hover bikes and saucers) were introduced to the series in Serious Sam 2. Vehicles feature turrets such as rocket launchers, machine guns, and laser turrets.[10]
The simplistic gameplay of Serious Sam 2 is similar to that of previous games in the series, but Serious Sam 2's lives system is a radical departure from the original games in the series (which would allow you to resume from checkpoints or saved games an infinite number of times). Although Serious Sam for Xbox was the first game in the series to feature a "lives system", Serious Sam 2 was the first PC game in the series to implement this system.[7][8][11]
Blood and gore effects have been improved relative to the previous games, and all enemies other than bosses can be gibbed.[12] Living foes can disintegrate into blood and bloody bits, undead entities, excluding Kleer Skeletons, can be reduced to decaying bits and slime, while magical creatures' destruction is marked with sparkle effects and purple gases. Power-ups are scattered throughout the game and can be obtained by destroying certain objects. The player is able to pick up certain objects and manipulate them in a manner similar to the effects of the Gravity Gun from Half-Life 2, though without the necessity of an external device.
While the game features various enemies seen in first person shooters, such as soldiers with chainguns, blasters and rocket launchers, there are also many other oddball enemies, like witches, clockwork toy rhinos, zombie stockbrokers with shotguns and suicidal exploding clowns. Different chapters feature native "chapter specific" enemies; for example the Kleer World features Flying Kleers and the Oriental setting of Chi Fang features Martial Arts Zombies. The players will also meet non-player characters (NPCs) throughout the game. There are five different groups of NPCs in the game: The Sirians, the Simbas, Zixies, Chi Che, and Elvians, each native to their respective planet. The different groups of NPCs help the player throughout the different settings of the game, with each group of NPC corresponding to a different setting in the game.
