Rez doesn't sound like much on paper (or Internet). You travel along a predetermined path using a lock-on mechanism to fire upon up to eight enemies at once. Blue power-ups gradually increase your health, allowing you to "evolve" into different forms, with successful enemy attacks reducing your growth by one stage of evolution, while red power-ups add to your stock of "Overdrives", which blitz whatever's in front of you when activated. There's a boss at the end of each of the game's five biggish levels, followed by a boss-rush finale that concludes with a bigger set-piece battle against an AI called Eden, which - if you're bothered about the fiction - it's your job to reboot.
But then Rez isn't trying to sound like much on paper (or, yes, Internet); it's much too busy focusing on how to integrate the game's splendid trance music soundtrack with the gameplay. Each level is broken into ten "layers", and with each transition to the next one the music intensifies. Individual sound effects are little synth stabs and drum beats, and the impact of your stacked lock-on projectiles, once you release the fire-button to send them on their way, is artfully delayed to match the underlying rhythm in a manner that rewards your senses. Playing well actually sounds good, which is why the game's commonly linked to the phenomenon of synaesthesia.
All this was true of the Dreamcast and PS2 versions of Rez, and for, Rez HD, developer Q Entertainment - headed up by original developer United Game Artists' Tetsuya Mizuguchi, of Lumines fame - has focused on sharpening the game's visuals and audio rather than building new levels or game mechanics. You can play the original version if you like, but unlike a lot of Xbox Live Arcade releases there's precious little sense in doing so. Once you've experienced the high-definition version with pin-sharp widescreen visuals and 5.1 surround sound (apparently not for the music though), going back to the boxy 4:3 standard version seems a bit silly. Whereas a lot of old-days code is included on XBLA to keep the purists happy, I wouldn't be surprised if Q decided to include it here just to show off.
As well it deserves to, because the sharpened lines of the game's environments - often seemingly based on ancient architecture despite their stylish, Tron-like wire-frame construction - are a much finer compliment to the game's imaginative artists than the pixellated alternative, and the game's broader image and the current prevalence of big-screen televisions mean that even people who know Rez inside out will struggle not to find themselves freshly enthused.
Undisturbed by the usual creeping desires to repackage and reinvent, a lot of Rez's subtler successes remain intact too - its well-judged difficulty curve, and the "travelling" mode that lets beginners work through it without the threat of death. The game's infamous Trance Vibrator (exactly what you're thinking, whatever Mizuguchi says) is no longer compatible, but single-player pad vibration is handled with restraint, and it's possible to plug in up to three additional pads so that anyone sitting near you can share the rhythm. Alternatively you could plaster yourself with pads, although we'll resist the urge to make any lewd suggestions - there are enough websites for that sort of thing anyway. The original's unlockables also return, and the XBLA version's 12 Achievements - while not quite as imaginative as some of their contemporaries - will certainly give you cause to return even after you've landed back on the title screen for a second play-through.
An understandable residual fondness has danced its way past the original main criticism levelled at the game in the early 2000s - namely that the experience was over within a few short hours and boxed videogames were not and still are not cheap. Q Entertainment's own experience with Xbox Live Arcade has evidently taught them the hard way how best to judge a game's modern worth though, because Rez HD is being lined up for an 800 Microsoft Points (GBP 6.80 / EUR 9.30) price tag, which seems perfectly sensible.
At that price, we'll probably end up advising existing fans to revisit it, and if this is all new to you and the idea of a game that inconspicuously binds a strong shoot-'em-up to music has you excited, we're confident you'll want to set aside those Microsoft Points whenever the game's released. Whispers from Microsoft point to late February, although Q remains quiet. Rez HD, however, does not; it serenades your senses in a way that a great many games since have struggled to emulate, and we'd like to see more of its kind on Microsoft and Sony download services in future.