Hidden is the eleventh Special Ops level in Call of Duty: Modern Warfare 2 and it is in the first in the Charlie tier of operations. The objective is to reach the extraction point, silently eliminating any enemies you find or avoiding them altogether along the way.
Hidden takes place in Chernobyl (after the disaster), and the player must navigate their way to the extraction point, which is where the level "All Ghillied Up" began, from the shipping container area, passing through heavily infested radiated areas. The player begins the level with an Intervention, which is suppressed, as well as a silenced USP .45 with Tactical Knife. There are silenced weapons at the start that are able to be picked up as well: the MP5KSD, the Mini-Uzi, the M1014, and the Striker. The game keeps track of how long the player takes to reach the extraction point and is also ranked on how efficiently they kill each individual enemy; the system used includes "Perfect" kills, "Good" kills or "Average" kills. This will not affect the star-based score that the player receives at the end of the mission in any way. The number of stars is based on the difficulty the player completed the mission on, regardless of the type of kills that one accumulated.
Grenades are very useful in taking out the Ghillie snipers. If the player wasn't noticed before throwing the grenade, and a sniper is killed by a grenade, it will still count as a Perfect kill.
Type of enemy/ type of kill
The player must kill a soldier without being noticed
The player has killed a suspicious soldier
The player has killed an aware soldier
The player must kill a sniper without being noticed