The original Dementium took me by surprise. One day I'm lounging around the office, twiddling my thumbs and watching chimps doing karate chops on YouTube, when Tom pops up and hands me a game. The box is fairly simple-looking - a plain red background with the title in gothic font. The blurb on the back tells me that it's a first-person shooter from an indie developer named Renegade Kid.

If I'm honest, I probably wasn't expecting it to be much cop. I certainly wasn't expecting what I found when I booted the game up - a thoroughly impressive FPS that seemed to push the DS to its limits. It had a creepy atmosphere, fantastic audio and horrible worm-like things that squealed like babies. I promptly wolfed down a slice of humble pie, apologised to the game for having doubted it, and immediately made a mental note to keep an eye on Renegade Kid.

The Texas developer has since released sci-fi blaster Moon, but for fans of the original there's only one thing that can satisfy their ghastly cravings: a second outing to their favourite Satanic hospital. Earlier this week Renegade Kid revealed the front cover to Dementium II - a picture of a bloke having his face crushed by a hand reaching out of his mouth. It's certainly a step-up from the simple red box we had last time, and judging from what I've seen of a preview build, the rest of the game will be similarly unhinged.

In simple terms, Dementium II seems intent on doing everything its predecessor did, but bigger and better. The DS cart will be twice the size as the first release, and the effect of this extra space is immediately evident: my first reactions to the new game included "Ooh, nice!" and "Look at the detail on that chest cavity!" During my half-an-hour demo I saw a wide variety of environments, almost as many as in the whole of the first game. You're still fighting through a hospital infested with evil creatures, but this time you'll find yourself warping back and forth between reality and a Silent Hill-style Hell. The game appears to be running extremely smoothly too - maintaining an impressive frame rate even with four or five enemies on-screen.

This guy must spend a fortune on dental floss...

It's also clear that Renegade Kid is keen to sort out some of the problems that held back the previous title. Dementium took a lot of flack for its use of respawning enemies and infrequent checkpoints, and while the latter issue was partly addressed for the game's European release, it was still far from perfect. This time enemies will only respawn in certain important areas, and you'll be able to save your progress any time you stumble across a mirror; I'm guessing that this symbolism will tie into the plot in some way, although it's not yet clear how. The in-game map has also been given something of an overhaul so that it now shows exactly where you've already been: if you pick up a key card or similar device it'll also highlight any doors that can be opened, sparing you from the tedium of wandering around like a lost tourist.

In addition to this, the game will frequently show you areas that you can't yet reach but will soon be able to. For example, one early stage features doorways that have been clumsily barricaded with wooden boards. As you can see through the slats it's clear that you'll be able to get past the barrier, but it's also obvious that you'll need a tool for the job. When you then discover a sledgehammer five minutes later, there's no mystery about what you're supposed to do. Aside from cracking open new doorways, the sledge also acts as a formidable melee weapon. You'll frequently be forced into close combat when ammo runs low, so expect to get well acquainted with both this and with the bloody shank you're handed at the start of the game.

While there'll be plenty of guns to play with, it's important not to underestimate the usefulness of a tool like the shank (anyone who's served a stretch in the clink would no doubt tell you the same). During the demo I watched as Renegade Kid's Jools Watsam used this makeshift knife to dispatch an early boss - a creature that resembled a huge, toothy mouth with the body of a stitched-together monkey. In addition to crawling about on the ceiling, this monster had a habit of projectile vomiting - an attack that requires the player to crouch. That's right, you can crouch this time; you can also jump and, most miraculously of all, you're now able to hold your torch and single-handed weapons at the same time. No more Doom 3-style fumbling in the dark.

I'm almost out of time, but I'd be doing Dementium II a great injustice if I didn't mention sound design. The original game gained a lot from the sublime audio, and it looks like the sequel will be even better. The story begins with you being wheeled from the operating theatre back to your tiny cell, and from this point you're treated to a cacophony of weird sound: insane patients gibbering freaky nonsense, security guards yelling out threats, and your very own personal nemesis: a mad doctor who taunts you over the hospital PA system. Oh, and the baby-voiced slugs also put in an appearance. It's hugely pleasing to see a developer pushing the DS so hard, and with any luck the final game should something of a treat when it arrives next year.

Dementium II will be released on the DS in 2010.