You can't beat a good conspiracy theory. Did you know that Tony Blair is from an ancient bloodline of alien lizard creatures? Presumably, Cherie's from a similar race with a crocodile bent, which would explain the toothy grin. All world leaders are blatantly aliens, anyway; they certainly talk in a different language in which it's physically impossible for the larynx to form syllables to answer a direct question.

This adventure game is based on the conspiracies surrounding the Tunguska event, which was a massive explosion that actually happened in Siberia in 1908. There's no doubting that it devastated a sizeable area, but what caused it is the subject of the inevitable theories... could it have been a weapons test, or an alien ship crash-landing? The game's developers have their own ideas, which you'll unravel as you progress, and the subject certainly makes for an intriguing plot-line.

Tunguska is a standard point-and-click adventure. The opening scenes make it clear that the dialogue has been translated into English, as it's a little clumsy and stilted, but bearably so. The graphics make a better initial impression - they're crisp and detailed - and the interface is a well-oiled, context-sensitive affair.

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Anything you can interact with is highlighted as you move the cursor across it, and you can examine with the right mouse button and use objects with the left. There's even a useful help button, which when pressed highlights all interactive objects, and this definitely comes in handy as some items are quite small and easily missed.

An adventure lives or dies by the quality of its puzzles, and there's a varied bunch here. Some are obvious, some are pleasantly logical and unfortunately some are downright daft. Let's look at a few examples (skip the next two paragraphs if you don't want to read small spoilers), beginning with an obvious puzzle. You pick up some batteries near the start of the game and a few minutes later you find a digital camera that doesn't work. Click batteries. Click camera. Tricky stuff.

Then there's the logical: a girl's bike tyre has gone flat and you need to repair the inner tube. You have a bicycle pump and can inflate the tyre, and nearby there's a bucket of water in which the tube can be immersed to find the hole, which can then be sealed up with glue and a patch made from some rubber gloves. The game's quite helpful when you're experimenting; for example, our first instinct was to simply try some glue on the hole, whereupon it hinted that we needed something to use as a patch, instead of just delivering a straight "That doesn't work" comment.

And then there are the daft puzzles. These include gems like Sellotaping your mobile phone to a cat and salting the pizza you're feeding it, so it gets thirsty and goes inside its owner's house to drink, allowing you to record his phone conversation on your mobile. Or our personal favourite: removing a rusted car jack which is wedged under a van by greasing it with - wait for it - a bread and butter sandwich. We kid you not.

There are definitely obscure and annoying moments where it's possible to get stuck, and matters descend into wandering around, continually pressing the help button to make sure you haven't missed anything and generally trying to combine everything in your inventory with everything else. But Tunguska isn't the first inventory-based puzzler to be guilty of falling into this particular hole.

By and large, though, the game provides a reasonable level of challenge, and enough in the way of help and hints to make sure you don't get brick-walled too often. Tunguska isn't anything spectacular, but it's a solid enough adventure with a reasonably interesting storyline.

Tunguska's a decent point-and-clicker, with a varied bunch of puzzles that occasionally stray into obscure or daft terrain. Luckily the slick interface and help features generally keep you on the right path, and the twenty pound price tag makes it good value for money.