Alien Swarm/Gameplay

Experience
After beating each mission, you will be awarded a certain amount of experience based on your performance during the level. By gaining experience, you will gain levels, which allows you to unlock new weapons and tools.

After completing the level, a summary screen is displayed which will show you how much experience was earned in specific categories.


 * Objectives Complete (max 1000): The 1000 XP is divided evenly between the objectives in the level. Finishing all the objectives will net 1000 XP.
 * Kills (max 100): Total number of enemies killed, irrespective of type.
 * Completion Time (max 100): Faster times earn more XP.
 * Friendly Fire Done (max 100): Each point of damage, inflicted by you or your sentries done to your team, will deduct one point.
 * Damage Taken (max 100): Each point of damage taken during the mission will deduct one point, regardless of healing.
 * Healing (max 50): As a Medic, every 10 health healed of a teammate will earn 1 XP, excluding Healing Kits.
 * Fast Hacks (max 50): As a Tech, you will be awarded 25 XP per fast hack.

Achievements
Each achievement completed during a mission will award 50 XP. Although unlocked only the first time achieved, many can be completed again for the experience gain.

Difficulty
Based on the difficulty of the mission, the total XP earned will be increased or decreased by a certain percentage:


 * Easy: -50%
 * Normal: No change
 * Hard: +20%
 * Insane: +40%
 * Brutal: +50%

Promotions
Once you reach level 27, you can choose to get promoted. Once promoted, you are returned to level 1 and all previously unlocked weapons are locked again. You will need to kill enemies to level up again, however the amount of experience required per level will be greater with each subsequent promotion.

An icon will be displayed beside your name once you reach each promotion level.


 * First Promotion: Titanium Star
 * Second Promotion: Carbide Star
 * Third Promotion: Gallium Cross
 * Fourth Promotion: Platinum Star
 * Fifth Promotion: Osmium Star
 * Sixth Promotion: Iridium Medallion