Fun is the trickiest of butterflies to pin. It's swift-moving and wayward; it never settles in one place for long.

Sometimes, it lurks in the past, with the memory of a staggering set-piece or the euphoria that bubbles up after a boss has been beaten. Elsewhere, it might wait for you in the future, threaded between the uppermost branches of a skill tree or hovering next to that Master Sword you aren't yet allowed to wield.

For Mario, though, it's always found in the present: in each jump and each backflip, each shattered block, and each squashed Goomba. Mario makes his fun in the here and now, and his games are defined not by set-pieces or unlocks, but by an endless, freewheeling playfulness.

In other words, they're defined by levels like Super Mario 3D Land's 8-1. Here I am, on the trail of the second of three Star Medals, and I've managed to get my head stuck in a question mark block. Isn't this awkward?

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I've punched maybe a million of these blocks during my time on Earth: you might say I'm something of an expert at it. Up until now, though, I've never had this sort of thing happen to me. Don't they know who I am? Don't the dungarees and the golden buttons ring a bell? They don't, apparently, so for the next few platforms I'm left to waddle around blindly, stomping Koopas, ducking spiked balls, and hiccupping money with every step. The entire incident lasts perhaps two minutes and 68 coins: just enough time for a brief muddling of the formula, and for a brilliant little joke at my expense.

"Super Mario 3D Land feels like the heir to Super Mario Bros. 3... The sense of connection is structural, almost textural."

Super Mario 3D Land feels like the heir to Super Mario Bros. 3, and it's moments like this that really drive that impression home. It's not just the Tanooki Suit, the music blocks, the pirate galleons or a handful of familiar tunes. The sense of connection is structural, almost textural.

Once again, the game's made up of short, gratuitously inventive levels filled with weird little asides and one-off gimmicks. The design is fuelled by tricksy ideas the same way the stages are built from sponge cake, icing sugar, and Custard Creams - and it's just the right approach to take after the exhaustive, gravity-bending dazzle of Super Mario Galaxy 2.

The plumber's last outing pushed the 3D platformer so far into the uncharted depths of space you could be forgiven for thinking the genre had just witnessed its own hectic eulogy. Now, Nintendo's brought things back down to earth with an adventure that could almost be called the Mario Variations - a game that plays like the Mushroom Kingdom equivalent of a tasting menu.

Mario 3's not the only point of reference, of course. 3D Land is willing to riff on any classic you can think of, borrowing the end-of-level flagpoles and destructible blocks from Super Mario Bros. while channelling Mario 64's wall-springs, Mario World's habit of hiding secrets in every corner, and even Mario Galaxy's easy way of subverting your most basic notions of what a platforming assault course should look like. Just when you think the whole thing's starting to settle down, you'll get a nasty surprise or two imported from The Lost Levels. It's a trip through the Mario museum, except the glass cases have been removed and you're allowed to mess around with each exhibit.

All these disparate ideas have come together to create an adventure that's been designed with bus journeys in mind, each stage compact and precise, like a colourful piece of corporate sculpture. None of the game's offerings will take you too long to beat, and - during 3D Land's first eight worlds, anyway - none of them will give you that much trouble, even if you've come back in search of that familiar trio of Star Medals. What they will all do, however, is surprise you, each hinging on a single gleaming gimmick, each moving to its own peculiar rhythm.

"All these disparate ideas have come together to create an adventure that's been designed with bus journeys in mind."

It's a game of a million pieces. There's the headline stuff like the power-ups, including that Tanooki Suit, which is every bit as energising and deadly as you remember - offering, like public drunkenness, that dangerous sense of potential that almost always terminates with a painful tumble off an unstable structure.

Then there are frisky bursts of pure geography, like the downhill level, the level that's all about cannons, and the really-big-thing-you-have-to-climb level. Enemies rope in Mario versions of the entire animal kingdom - everything from giant eels to spiked water-boatmen and horrible sand-burrowing slugs - while guest stars include the likes of Dry Bones, Mario 3's terrifying monster fish, and Kamek, who still defiantly fires the PlayStation button layout at you, safe, perhaps, in the knowledge that Nintendo got to it first.

On top of all that, the 3DS brings its own share of gimmicks, with a fair number of sequences where you plummet down through the atmosphere, race away from an avalanche of spiked boulders, or engage in gentle Escher-style perspective puzzles as you pick a path across chunky towers of bricks. The use of 3D is as restrained as it is successful, though, and for the most part the illusion of depth is simply employed to make one of the most tangible worlds in games even more physical and convincing.

Expect caverns chiselled from hard candy where you can see bright secrets glinting in the deep. Expect rugged castle peaks poking through tufts of clouds. One level - another throwaway, of course - uses the console's lenticular screen to recreate the echo-y top-down dungeons of the first Zelda, right through to the stone-clad fire pits and a handful of classic sound effects.

It's an astonishing moment, but it's quickly lost within the endless rush of creativity. Seconds later, Hyrule's forgotten, and you're off on another trail, marvelling over the realisation that you can blow into the microphone to disperse dandelions, or wondering in bemusement how the outside of a Toad House can be round while the inside is square.

"This is roughly twice the game it initially appears to be."

Curiouser and curiouser. 3D Land may be blessed with a powerful sense of forward momentum, but don't let that trick you into thinking it's in any way insubstantial. Sure, you can complete the initial campaign in around six hours, and that's without rushing. But if you're disappointed, that's probably because you're assuming it's the only campaign 3D Land has to offer.

In truth, Nintendo's just getting started. In truth, the very best stuff is yet to be discovered. It would be a spoiler to explain how, but in a very real sense, this is roughly twice the game it initially appears to be.

Even after you're 12 hours in, there's a nagging sense that the whole thing should actually be falling apart, though. Shouldn't all of these ideas, each tugging in their own direction, make for an incoherent adventure that feels like a slog through a densely-layered scrap heap?

What ties 3D Land together, however - what ties all Mario games together, in fact - is Mario himself. Nintendo's plumber doesn't just move through the game's levels: he completes them, providing the crucial element that unifies the design and keeps the entire thing standing.

It's his jumps that make the flipping panels of 2-4 switch from blue to red, allowing him to follow an intricate racing line that's been scribbled across the landscape. It's his squishy little body that triggers the unfolding green switch-plates that go click-clacking into the sky, building bridges, staircases, and even entire pyramids for him to clamber over. In Bowser fights, Mario's running speed sets the pace for the onslaught of the fireballs. In ghost houses, he creates the geometry he needs just by leaping into empty space.

The best levels on offer feel like musical sequencers, in a way, with Nintendo's hero standing in for the all-powerful timeline, smoothly triggering events as it sweeps along and turning a formless congregation of single notes into a tune. It's the epitome, in other words, of the player-centric video game.

This is the one idea that competitors can never quite get to grips with, the single, crucial element they can't clone. It's also why Mario is such a hard act to beat, even if individual parts of his games don't always live up to the heritage.

3D Land is great, but it isn't perfect. Compared to the fluffy, nostalgic warmth of the Tanooki suit and its twin, the Statue Leaf, both the Boomerang Flower and the Propeller Box feel like missed opportunities, the former making for a slightly fussier take on the Fire Flower, even if it is good for capturing distant trinkets, just as the latter remains firmly under the shadow of New Super Mario's various whirligigs.

Seasoned players, meanwhile, will get through the first half of the game a touch too quickly, finding much to enjoy but little to truly challenge them. It can feel, for a few hours at least, like a very slight disappointment.

Is 3D Land too easy for too long, then? That's an impossible question to answer, really, because most of us are Mario experts by this point, capable of being summoned to Whitehall at a moment's notice to brief the coalition government on oddities like the Goomba Boot and the difference between successfully dispatching a Piranha Plant and a Chain Chomp. (The former you hit on the head, the latter you hit on the tether, obv.) If you've been playing Mario since 1985, yes, you're going to get through a lot of this at speed and with little sweat. If you're an eight-year-old, however, lucky enough for this to be your introduction to the series, there's going to be plenty for you to master in this rich and complex world.

Even for the experts, some of the game's later stages are gleefully malevolent and filled with the odd standout shocker. That's the truly astonishing thing about Mario, when you get down to it. Despite the in-jokes and the endless self-referencing, despite the cameo appearances and the antic reinvention of old ideas, in some central way, each Mario game feels like the first.

Each presents itself like the work of a brilliant young team getting every idea it can think of onto the screen, and refusing to rely on any kind of cheap crutch. Can you imagine a QTE boss fight slapped on top of a core Mario game? Can you imagine an XP system stuck through the middle to make it last a little longer?

You could wish for 3D Land to be a little more challenging in places, then, but you couldn't wish for it to be any denser, any more imaginative, or any more daring. Most importantly, you couldn't wish for it to be any more playful.