Fathom =----- At last... an original game theme! I must admit to becoming a bit jaded with the usual video game fare of shooting aliens, dodging ghosts or blasting tanks. OK - so I'm probably generalising a lot. But Imagic's latest for the Atari VCS struck me with its originality.

Here's the general idea of the game. An evil undersea race, the Titans, have imprisoned Neptune's daughter, the beautiful mermaid Neptina.

You take the part of Proteus, a member of Neptune's watery royal court, and set off to rescue Neptina from the underwater cage the Titans have built as a mermaid trap!

Proteus takes the form of a dolphin to avoid the attentions of the Titans - but he can also change into a seagull to patrol the skies above the oceans.

The aim of the game is to help Proteus find the three pieces of Neptune's missing Trident - as only this can free Neptina from the Titan's cage.

The keys to finding the bits of the Trident are magical starfish in the sea and stars in the sky. To discover these, Proteus the dolphin must touch seahorses in the sea and, when disguised as a seagull, Proteus must touch pink clouds in the sky.

Touch enough seahorses or clouds and the magical stars and starfish are revealed. Touch the stars and starfish and Proteus gets one of the missing bits of the Trident.

But there are enemies in the sea and sky - nasty octopii and intelligent bits of seaweed hinter the Proteus' search underwater, while backbirds patrol the skies.

Once you've managed to get the Trident and rescue Neptune's daughter, you move onto another level, which opens up new horizons. Your seagull has to fly further to get those all-important stars and the dolphin has to dive deeper to get the starfish and seahorses. All the time you have to keep an eye on your energy level. Touching seahorses and clouds keeps you energy high - but hitting an octopus, seaweed, blackbird or black cloud drains your energy.

Fathom is a game of strategy and action. You need to work out the best time to transform from bird to dolphin and vice-versa, where to find the starfish and stars, and how to keep that energy level high enough to keep going.

The graphics must be among the best around for the VCS - although the sound effects are a bit limited.

The game is well presented with an informative instruction leaflet which includes tips on how to survive the first level of the game - invaluable for a beginner attempting to get into the game for the first time. You do have to read the instructions carefully to get the most out of the game.

This leaflet promises a special surprise if you manage to free the mermaid Neptina seven times. I can't wait!

Fathom is available now from Imagic and can be found at all Atari video games stockists at £29.95.