Campaign scoring

Campaign Scoring, also known as Meta-game, is an optional game feature for the campaign mode of Halo 3.

When playing with Campaign Scoring turned on, the player plays a normal campaign mission (single player or cooperative), but progress is scored with points for notable activities. Having skulls activated increases the amount of points gained, as well as accuracy and kill count. Different enemies give different points as do headshots (and assumably any other kill that would be worth a medal). Betrayals will cause negative points so cooperative work will be necessary. To find out more about campaign scoring, listen to mission Design Lead Paul Bertone on the Bungie podcast.

Free-for-all vs. Team Scoring
In Free for All scoring, points are awarded to individual players based on their kills. Points earned in this mode can be used to unlock the meta-game achievements.

In Team Scoring, points are shared among the team, culminating in a cumulative team score.

Point Values
Points are earned by killing enemies, with the player shooting the killing shot (or throwing the killing grenade) earning the points. Following is a list of base points earned for killing enemies (i.e. without any multipliers).

Difficulty Multipliers
Overall

Skull Multipliers
Overall

Time Multipliers
Overall

From 3.0x to 1.0x, decreasing by 0.5x as time passes.

Style Multipliers
Per-kill

Scoring Formula
The Formula for Campaign Scoring is:

Points Earned = Unit's base point value X (Style Multiplier + Occasional 2nd Style Multiplier) X (Difficulty Multiplier + Skull Multipliers) X Time Multiplier

Achievements

 * Guerilla unlocked by earning 15,000 points on Sierra 117
 * Demon unlocked by earning 15,000 points on Crow's Nest
 * Cavalier unlocked by earning 15,000 points on Tsavo Highway
 * Askar unlocked by earning 15,000 points on The Storm
 * Exterminator unlocked by earning 15,000 points on Floodgate
 * Ranger unlocked by earning 50,000 points on The Ark
 * Vanguard unlocked by earning 50,000 points on The Covenant
 * Orpheus unlocked by earning 15,000 points on Cortana
 * Reclaimer unlocked by earning 15,000 points on Halo