This level begins in a blizzard and halfway up a mountain, with you edging around a tiny ledge with your back to a sheet of solid ice and your front to countless fathoms of fresh high-altitude air. What follows is a remarkable set of stunts, climbs and perilous dangling as you follow Soap up the ice sheet - a subtle mix of player-controlled movement, predetermined slips and acrobatics.
You'll slam ice axes into the glacier with your left and right hands through alternate mouse clicks, hauling yourself up and watching the ice crack as you put your weight on it. You'll watch Soap heroically leap a massive gap with ice axes flailing (in the manner of the only good bit of Vertical Limit), then do so yourself before the ice breaks beneath you and Soap dashes to grab your arm.
This is all far removed from what you'd expect, and an example of the way Infinity Ward are manhandling a multitude of different experiences, peaks and troughs into each and every level. Always ensuring that you'll never know what to expect. What you should expect next is a two-man stealth assault on an enemy airbase. A blanket of fog rolls in and out, while flurries of snow covers all so you can just about see the silhouettes of patrolling guards, beautifully animated and hunched against the elements, and the red glow of their cigarette butts.
What pans out is similar to the early stages of the assault on Chernobyl in COD4, moments such as the memorable "You take the one on the left on the count of three" trick are elegantly woven into the level's gameplay and are no longer stand-out moments. You're even equipped with a heart-beat sensor, and can make out where your prey are patrolling - and soon Soap retreats to a sniping position to help you take out the periphery soldiers.
Again, this leads to semi-scripted moments of utter genius - such as Soap lining up a kill and saying "I've got this one..." the second before you launch into a melee attack, taking out his target and leaving him to mutter, "Oh... never mind." Small details like this pepper the game, even more so than in the original, and the result is a smooth and organic experience where you simply can't see the joins.
Eventually, having perched explosives on the required targets, you meet up with Soap and venture inside one of the airfield's hangars. It's at this point that the ever-evolving gameplay of the level turns from sneaking and stealth, and enters the familiar Call of Duty phase in which the shit hits the fan and you find yourself involuntarily hiding behind the scenery just to catch your breath. You run up to the hangar gantry, and look over the building's floor to see Soap with his arms raised and around 20 Russians at the, now open, hangar doors aiming their guns at him (GoldenEye comparisons begin here).
At first you assume he's a goner, but then the game casually reminds you that you've got a detonator in your hand and Soap soon makes his escape alongside billowing smoke and flame. "These moments of peak gameplay are more punctuated, they stand out more, when you have quiet moments that lead up to them," Zampella says, standing on the now mist-free runway and watching soldiers flood in from every direction towards him; MIGs and fuel tanks exploding nearby in the crisp mountain air. "We go for peaks and valleys in the gameplay. We make the whole game that way, but within a single level we do the same thing."
As Soap and the player leg it over the runway with every available evil-minded Russian on their tail the distant reedy engines of enemy snowmobiles can be heard: "It's not our game unless there's eight different games inside of it..." explains Bowling, as three Ski-Doos leap over the crest of a hill towards the player.