The best things come in small packages, or so they say. 82.1% of us at gadgetshop HQ thought this frivolous mumbo-jumbo until we encountered the sleek, metallic and utterly beguiling NKryptor puzzle from the same clever types who brought us the dastardly Isis a few years back. It might only be the size of an audio cassette tape, but beneath its hand-crafted exterior of high grade aluminium, there lies a bonus PC game offering the chance to win everything from iPods to LCD televisions. (Product key verification is required at this stage).

The challenge, however, is not just to win the game and enter the prize zone beyond, but to actually find a way into the Egyptian-themed box in the first instance. Here, as the laser-red eyes of the sphinx glare out at you, a touch of brain over brawn is the order of the day - for getting into the box requires more in the way of grey matter than muscle power. They say that the exterior metal housing was invented by a magician, but opening his creation needs the application of a serious mind, not smoke and mirrors.

The NKryptor - infuriating, beautiful, and most definitely a sphinx with a riddle, had us captivated for days on end. Beware. It will cast its spell over you, too.