Penumbra: Overture is a scary game. It might stumble at various points and suffers from a rather ambitious physics-based interaction system, but you can't escape the fact that you're heart will be racing within five minutes of starting. Set in almost complete darkness for its entirety, Penumbra mixes adventuring with first-person action, throws in numerous puzzles and just about comes out smelling of roses - even if they have been trampled by zombie-like dogs.

Thrown into an underground tunnel system, you're left to find out just what's going on and to figure out how you're going to get out - the ladder down can't be reached on the way back out. There's a story that runs through the entire game, but it's rather clumsily told and more often than not gets in the way of the nail-biting tension and fear that lurks around every darkened corner. The small development team would have been better off focussing almost entirely on the eerie setting and, more importantly, the combat system.

Combat is by far the weakest aspect of Penumbra, offering what can only be described as a clumsy, hit and miss, gesture-based system. To be fair, early on you're told that it's best to avoid combat, with stealth being the recommended option, but at times it's unavoidable. Waving your mouse around to jab or prod your weapon makes successful attacks as likely as being able to see more than two feet in front of your face.

Stealth is handled well, with your vision turning purple when you're hidden, but an on-screen radar to show roaming enemies is sorely missing. While it might have lessened the immersive atmosphere, there's only so long that you can wait, cowering behind a crate, before it becomes rather dull. And you will wait. With no quick save option, death throws you back to a checkpoint that can be some way back, so if there's a wolf on the prowl you're going to be damn sure that it's gone before you step out from the darkness.

Interaction is where Penumbra really succeeds, with your on-screen pointer/hand able to touch and move objects realistically. Be it the simple action of opening a door or drawer by pulling it towards you, or pulling a set of shelves over to reveal a hidden passage, it feels good. Rather than simply running around a room and pressing a button to check out each and every item, you actually interact with the environment and this makes the believability of the environment even greater.

As you progress you'll be asked to do far more than simply turning an object, but the developers have used the old "this door is locked" route far too often. You'll have to find alternate routes in and at first this poses a challenge simply because you're not used to having the level of interactivity that is on offer. Early on there's a box of rocks and you might think nothing of it. But empty that box and you can then pull it aside to reveal a hatch. It's simple stuff, but clever at the same time.

Without a light of some sort, you'll be exploring in the dark.

For every clever puzzle, with clues given by Morse code or similar, three's a locked door or obvious code given in bold letters on one of many documents found lying around the environment. It's certainly uneven, with moments of brilliance separated by genre staples, but as a first of a trilogy of short chapters, the road ahead looks very promising.

Certainly, in terms of visuals and audio, Penumbra falls someway short of what modern PC gamers expect, but the physics system is great and the dated visuals don't hurt the atmosphere one bit. Audio work is good too, with unsettling murmurs and unexplainable groans peppering the quiet, but voice over work feels amateurish and sentences often end a split second before they should.

It's hard to be overly harsh on a game created on such a small budget and with a team a fraction of the size of those found at behemoths like EA, but Penumbra is still a game that costs money to play. Available for less than £10 online, the many great physics-based puzzles and unrelenting feeling of fear are well worth the asking price, but don't expect a game that will compete with multi-million pound projects.