Operation Mecha Engine

Operation Mecha Engine is an advanced difficulty tour for Mann vs Machine, added on December 20th, 2012, as a part of the Mecha Update. It consists of three missions across two different maps. Operation Mecha Engine introduced a new map, named Big Rock, and added in Engineer robots to the robot army.

Decoy

 * Disintegration

Big Rock

 * Broken Parts
 * Bone Shaker

Rewards
Completing a mission in Operation Mecha Engine will reward the player with a random weapon, robot cosmetic, or item. Completing all three missions will reward the player with a Silver or Gold Botkiller Mk. II Weapon (alongside the standard random drop).

Upon completing your first mission in Operation Mecha Engine, you will be given the Operation Mecha Engine Badge. The badge will track your current tour progress, and will gain a level each time you complete an Operation Mecha Engine tour.

Disintegration
The mission consists of many melee robots and it is reccomended to use a longe-range class like the Heavy, Sniper, Demoman, or Soldier. This missions does however have a boss battle: Major Bomber. It is recommended to handle from up close if you can take the damage or from a distance and behind cover if not.

Bone Shaker
This mission isn't too hard but it has demoknights which are just as powerful as the spawned Scouts, Heavies and Soldiers. It also features scouts with "Bonk! Atomic Punch" as a weapon. The boss is named Captain Punch, but the range is melee so engineers, demomen and heavies can take down the boss from a distance.

Broken Parts
This mission has Bonk! Atomic Punch scouts, giant soldiers and uber medics on the first wave. And it gets HARDER! Much harder. The final boss is Sergeant Crits, an improved version of the Giant Burst Fire Soldier. Have one player playing the role of lure, either a Scout, an Engineer or a player with ÜberCharge canteens, while the others focus fire on the boss. Keep an eye on the large squads of support robots helping Sergeant Crits!