There's an area in Sonic 2's Chemical Plant Zone that still has me clutching my chest when I think of it. Tucked towards the end of the second act is a shaft filled with moving blocks, sliding around in clumps of four to create a precarious series of stairways. Nothing too horrendous in itself, but as you climb to the top the zone's underlying ocean of toxic purple goop surges abruptly, flooding the shaft even as the door slams shut behind you. Is there any track in all of video game music more nightmarish than Sonic's drowning countdown? And is there anything more dreadful, when you're in the teeth of that music, than having to wrestle with the game's underwater physics - wilting in horror as you graze a block by a pixel, precious seconds squandered as the blue blur drifts lazily to the platform beneath?
That flooded shaft kept my eight-year-old self from the relative peace of the Aquatic Ruin Zone for months - and it's back in Sonic Mania, Christian Whitehead's absurdly lovely homage to Sonic's 16-bit heyday. Much else has changed, however. Dotted throughout the 2017 incarnation of Chemical Plant you'll find power-up TVs lifted from Sonic 3 - including the Bubble Shield, which staves off the threat of suffocation. Entire sections of the course have been uprooted, rearranged and spruced up with new fixtures, such as troughs of gel you can harden into bounce pads by jumping on giant syringes. And the bosses, above all, have been completely reimagined. I won't spoil it, but Act 2's concluding clash is the kind of gleeful nod to a certain other Sonic game that should have any long-in-the-tooth fan laughing hysterically. It's representative of a project that doesn't merely restore the past with the care of a museum curator touching up a faded portrait, but also twists and expands it, to create an experience that is equal parts nostalgia pang and giddy excitement.
To put that in slightly less grandiose terms, Mania is Sonic without 20-odd years of slowly accumulating bullshit. The wider pantheon of sidekicks - Shadow, Silver, Big the sodding Cat - have been cast headlong into the screaming cosmic abyss from whence they came, reducing the playable line-up to the Holy Trinity: Sonic himself (who can use each shield power-up's special ability), long-suffering fox acquaintance Tails (who can fly and swim) and beefy echidna rival Knuckles (who can smash through certain walls, climb and glide). The game's 12 zones mix comprehensive, extremely playful reworkings of classic levels from Sonic 1 through Sonic & Knuckles with three brand new stages - all designed by Whitehead, fellow Sonic guru Simon "Headcannon" Thomley and Major Magnet studio PagodaWest using the Retro Engine, a proprietary technology built specifically to support features from the 32-bit console generation and before.
It all boils down once again to collecting rings, bopping robots created by villainous Dr Eggman, scouring Special Stages for Chaos Emeralds and toying with the mercurial possibilities of vast, ornate, helter-skelter levels, each an intoxicating contradiction: on the one hand, a glittering accelerator and on the other, an elaborate death trap, where no 200mph leap is complete unless there's a wall of spikes at the other end of it. It's intriguing to revisit an experience as violently, exhilaratingly unfair as 16-bit Sonic today. One design concept that commands a lot of regard at present is "flow" - briefly, that supposedly Zen-like state of heightened appreciation when a game is just challenging enough to keep you hooked, but not so challenging that you lose patience. I can't imagine anything further away from that than the average 2D Sonic level (on your first attempt, at least), thanks to the infuriating way Sonic works against itself.
The game's exquisite pinball handling and smooth-scrolling raster graphics are an incentive to let go, to revel in the sense of velocity, but to tumble down even the gentlest rise is to risk being sucked into a series of loops, ramps, warp tubes and bumper pads - power-ups fleetingly, tantalisingly visible in alcoves as terrain traps loom out of screen-right. For every second you'll spend plunging through the infrastructure you'll spend another jumping frantically to scoop up dropped rings, following a head-on collision with a malevolent drone. It's certainly an acquired taste, next to the stately unfolding of the average Mario game. People call Dark Souls vicious, but Sonic was getting himself launched into turbines, squashed by pistons, incinerated, electrocuted and scythed out of the air when the Capra Demon was just a baleful glimmer in Hidetaka Miyazaki's eye.
Why would any newcomer bother with such a bruising experience? Well, in part because there is simply nothing like the thrill of Sonic travelling at top speed, curling into a ball so that your momentum takes over, the course tunnelling down into the bedrock only to double back and fling you towards (if you're lucky) a stratospheric tangle of rings. There's joy, too, in the act of resisting the game's heady onward rush, skidding to a halt in order to search for an alternate route, chase down a power-up or smash through a partition to expose a giant ring (which serve as portals to special stages). The environment assets themselves, new and old, are certainly worth lingering over. Sonic CD's Stardust Speedway is a gilded mesh of vines and trumpets, criss-crossed by hazy spotlights; sadly, you can't experience each act in multiple timeframes, as per the original, but it's a bewitching creation nonetheless, with a familiar foe glowering at the end of it. The Mania team's own Garden Press Zone, meanwhile, is an elegantly daft hybrid of feudal Japanese temple and what looks like a Victorian papermill, newsprint flashing through its backdrop layers.
If new players will fall in love with the game's sheer opulence and aesthetic quirkiness, the glory for a returning fan is to explore how the familiar has been rendered unfamiliar. One of Whitehead and co's most inspired decisions is to enact a sort of creative dialogue between each Zone's acts - the first serves to reintroduce a classic setup with a few additional flourishes, while the second spins the concept out in a beautifully flamboyant direction. The second act of Sonic 2's Oil Ocean, for example, now has you dealing with the effects of a conflagration sparked by the first act's bossfight. The Flying Battery Zone from Sonic & Knuckles now suffers from increasingly inclement weather, rendering traversal of the vessel's enormous hull extra-hazardous towards the finale. There's equal delight to finding props and enemy types from certain classic layouts transported into others, or old tricks probed mischievously for additional knock-on effects. The lightning shield now glues you to the ceiling in certain areas. The flame shield burns through wooden platforms and sets flammable substances alight.
The game's special and bonus stages are, as ever with Sonic, its wobbliest components. The latter scrub up OK - taken from Sonic 3, they see you running around a grid-based globe map collecting blue orbs and rings while avoiding red orbs, your speed increasing by fixed increments. The special stages, however, are a mixture of Sonic CD's equivalents and elements from the scrapped Sonic Saturn; they see you chasing a UFO around an F-Zero-style course, gathering blue orbs to accelerate and rings to add seconds to the level clock. Decent-enough fun in short bursts, but the slightly characterless handling is a reminder, perhaps an appropriate reminder, of how ill-suited Sonic's breakneck formula would prove to 3D platforming.
All that's swiftly forgiven, however, the second you dive back into the main game. Mania takes everything that was memorable about Sega's pioneering 2D platformers - that joy in momentum always teetering on the brink of disaster, the deranged magnificence of those levels, the mournful bassnote as poor, faithful Tails stampedes into all the traps you've just triggered in passing - and rejuvenates it, to the point where you can only put down the pad in astonishment. Sonic the Hedgehog happened, everybody. He's supposed to be all washed up - gaming's Birdman, a balding, leather-jacketed C-lister they wheel on whenever some Mario crossover finds itself short on backing characters. How the hell is this possible? It's possible because for a small group of dedicated aficionados, the blue blur's halcyon period never ended. What's old has become new, and Sonic is once again the star he was supposed to be.