Marine Experience

Marine Experience is earned in-game and used to level up your character. New players will quickly learn that Marine XP does not carry over between games. Each new game a player starts with no Marine XP, and must reacquire it every match.

Global Experience
Several instances reward all players on the team a large amount of marine XP. These events are usually important points in a campaign, or to offset level up differences created between various characters. The following are some common examples.
 * Infestors: Each Infestor killed rewards 100 Marine Experience to all players, or any player's pet.
 * Bosses: Most bosses will reward all surviving players or pets a large sum of experience when defeated.

Kills
The vast majority of a player's Marine XP is generated by his kills. Each kill rewards the player a set amount of marine xp, based on the type of enemy, to the player who scored the killing blow. Exp from kills is not based on total damage dealt, or any other variable aside from scoring the damage that killed the enemy. Allied Units do not award Marine Exp if killed, although some neutral units, ie, Explosives do actually yield a very minute amount.

Shared Experience
Marine Experience is shared to better facilitate even leveling among classes and encourage teamwork. When a player scores a kill, he/she will receive 100% of the Marine Experience from the kill. However, allied players (and some Allied Units) that are nearby also receive a portion of the experience value of the enemy. Because of this, sticking together and not attempting to run off and steal kills will yield higher total amounts of Marine Experience earned. As players remain huddled in close proximity they will each receive the shared exp reward for all their nearby allies. Likewise, they will give all nearby allies the share from their kills. Because of this, a maximum amount of Marine Experience is being awarded to all players.

Minion Units
Minions such as the X1 Guardian and Reaper Drone will reward 75% Marine Experience to their master player. Minion Units that have their own level up system, such as the Forward Observer Mobile Infantry & Reaper Drone also award 75% experience to that actual unit, effectively created "175% experience" per kill, as both the host and the minion are awarded full marine experience but the experience from the minion is cut by 25% when awarded to it's master player. This 25% cut does not affect the shared experience pool to nearby players. These minions also give a smaller than average amount of shared experience to nearby player characters.

As an exception to this rule, Ivan & Ogilvy gives 100% of his marine experience to the player he follows, and does not give shared experience to other characters.

NPCs
Units allied to the player characters, but not directly controlled by them will also reward shared experience. When an allied unit kills an enemy, it takes the full amount of experience for itself, even if it lacks a level up system (such as the M1A8 Abrams tanks); however, it will award a larger than average amount of shared experience to nearby player characters.