Think back. You're ten years old and in an arcade, playing Time Crisis while a friend watches. You press the pedal to pop out from behind cover, take down some bad guys - soldiers, terrorists, it doesn't matter - and then duck back down. You think the story has something to do with a Vice President, but you don't really pay attention during the story parts. "Wouldn't it be cool if you could walk around, instead of just shooting?" says your friend, idly. That would be cool, you think, but then you die in the next area and, out of money, go home.

What you didn't know is that, back at the arcade, Dr. Peter Callofduty overheard your conversation, and he's just had an idea.

While fighting through the streets of New York, Paris, London, Prague, Berlin and more in Modern Warfare 3, I keep coming back to this. If you compare the Call of Duty series to, say, Skyrim, or even Half-Life 2, then it's a regressive, controlling, anti-gaming experience. Don't compare it to those games, then. Modern Warfare 3 is an arcade rail shooter, except you can control your legs a bit.

It feels this way because, for the first time, Infinity Ward have got the scripting right. Modern Warfare 1 and 2's bombastic scenarios frequently left you in the dark, unsure whether progress meant killing all the henchmen or tripping an invisible barrier to stop them infinitely respawning. In Black Ops, wild over-scripting left you feeling unnecessary; whole levels seemed to pass without you needing to fire a shot.

Here, you always know what you're doing, and the answer is almost always the same: reach the marker while killing everyone in your path. Or, for a change of pace, follow this other person while killing everyone in your path.

That's unfair. Sometimes it's: mount this gun on a side of a helicopter or car and kill everyone in your path. As long as you keep moving forward, the fantasy never breaks.

That pace is a change from previous Modern Warfare games that means there are fewer stand-out or game-changing missions. Instead of a quiet, prolonged stealth section, like Modern Warfare 1's Pripyat, moments of sneaking are shorter and peppered across the game. A lot of the missions now have their own self-contained arc: a sneaking opening, a disaster in the middle, and then a daring escape.

Taken individually, that makes each mission a satisfying experience. As a whole, it makes the game feel monotone, relentless, exhausting. By its end, I had killed thousands of people, each with the same set of rattly machineguns.

There are two moments that do stand out from that, one good and one bad. The good has you tumbling through a plane as it falls from the sky. With each turbulent shake and twist, you and your enemies are hurled into the walls, or cast weightless as you try to line up a shot with your pistol. The whole sequence lasts around 90 seconds, and it's brilliant.

The bad moment is optional. There's a warning message at the very start of Modern Warfare 3. "Some players may find some game content in one of the missions disturbing or offensive." You're asked if you'd like to skip that content, with no idea what it really is, and the options are "Yes, ask me later" or "No, I will not be offended."

I lied and chose the latter. I had already watched the scene, set in London, in which an American child is blown up. You're the father of the family, filming the scene, and your wife turns to you and says, "Are you getting this?". She's waiting for you to move closer. The explosion doesn't happen until you do.

It's crude, leering, pathetic, terribly written, and a cynical attempt to court headlines. I walked towards my family with the camera pointed in the opposite direction, killing us all while I filmed the side of a phonebox.

The rest of the singleplayer isn't so cynical. The events of Modern Warfare 2 - particularly the dismal "No Russian" mission - have tipped the world in to all out war. You again play Captain Price, Soap McTavish, and other soldiers from America, Russia and Britain as they try to finally stop the supervillain, Makarov.

When the story interjects in between shooting, like a Time Crisis "WAIT" command, it's complete gibberish. Example: why is that American family holidaying in London while their country is being invaded by Russia? But these moments are always brief, quickly setting up the next violent sprint. Everyone you meet has a gun glued to their hands, but it doesn't feel as objectionably aggressive as some of its peers. The experience is so straightforward that, although sometimes dull, its seven hours of stupidity feel almost good-natured.

In all my experiences so far, the multiplayer is similarly good-natured. My time with Modern Warfare 2 was spent mostly being blown up from the sky, being stabbed in an instant from a dozen feet away, or being made fun of for sucking. Every game of Modern Warfare 3's multiplayer, by comparison, has ended with a flurry of "gg"'s.

I've probably just been lucky, but the changes Infinity Ward made are all designed to make multiplayer a fairer and less frustrating experience. It has worked.

Terrible ideas like the Commando perk, which let enemies zip towards you with a knife in an unavoidable dash, are gone. Killstreaks have morphed in to Pointstreaks, giving you rewards for capturing flags and helping your team as well as for popping heads. If you don't have the world's best aim, you now have some hope of getting the occasional space-missile anyway.

The biggest improvement comes through the level design. The traditional Call of Duty multiplayer map used to be slaughterhouses lined by a dozen windows and doorways, with inexperienced players as the stunned cows trapped inside. Now they're designed to keep people moving, each area flowing in to the next, without the cubbyholes for snipers to hide inside. I haven't yet found a level I dislike, although the German shopping mall "Arkaden" is my favourite.

Whatever map you play, the progression system rewards you quickly and constantly. I reached level 5 in an hour, and level 10 ninety minutes after that. After almost every round, I've unlocked something new, be it a weapon, an emblem or entirely new game mode.

Of Modern Warfare 3's new modes, Kill Confirmed is the one I'm enjoying most. It's an old idea, but it works: every time a player dies, they drop a dog tag. For a kill to count towards your team's score, you need to collect your fallen enemies tag. Similarly, if you collect one of your own team's tags, you deny your enemy the kill.

While the other modes can either feel aimless or messy, Kill Confirmed gives your shooting purpose, and creates a kind of ambient teamwork. It's also dramatic, as players make desperate dashes across open ground to recover a comrade's tags and deprive the enemy.

These moments of drama are exactly what the rest of Modern Warfare 3's multiplayer is lacking. For the most part, whatever the mode, all you do is run around and shoot people. There is no spectacle, there are no last-minute reprieves or desperate pushes. It's fast-paced killing with rattly machineguns, with only the upgrades to provide the compulsion to keep playing.

If you want purpose to your multiplayer, the co-operative Spec Ops mode is probably the best way to experience Modern Warfare 3's thrills. There are two types. The first is the new Survival mode, in which you fight against escalating waves of baddies. After each wave, you get money that lets you buy new weapons, place mines and call in airstrikes. It's simple and challenging.

The second mode sends you in to remixes of the singleplayer campaign's key missions, as the attackers in that aforementioned plane assault or as soldiers assaulting a submarine. You likely won't succeed your first time through, but gradually, as you try again and again, you and your partner fall in to step with each other. Even when playing with strangers online, we've quickly become an efficient world-saving robot. Playing this way skips the hackneyed plot of the singleplayer, beats its boredom with brevity, and provides clearer teamwork and direction than the mayhem of the multiplayer.

Call of Duty games have always followed a simple formula. Your side-of-the-case instructions in singleplayer are "shoot men to save world", and in multiplayer it's "shoot men to unlock rewards". But previous games have cluttered that formula with terrible game design, from frustrating scripting to unfair balancing.

With Modern Warfare 3, it feels like they said, "Hey, let's stop putting in bullshit." To which someone replied, "Sure. Let's mostly stop." Modern Warfare 3 is linear, badly written and one note. It's still, from a certain angle, regressive. It's also fun.