I've clocked up 26 hours so far - not consecutively, I hasten to point out - and I doubt I'm even halfway there.

Pokémon game cartridges have always been coloured to match their name - Red, Blue, Gold, Silver - and Ruby is no exception, coming in a nice tranlucent red that really makes the cartridge stand out among its black or grey brethren.

The manual is much thicker than most. You could dive straight in without reading it, as characters and signposts in the game give lots of hints and tips, but I'd recommend a thorough perusal to get maximum enjoyment out of the game. As well as giving you your character's backstory and telling you how to set options like text speed, the manual contains the Braille alphabet (which apparently turns up in the game though I haven't encountered it yet) and tells the reader 'you could even find Braille in your home town'.

How brilliant is that? For a game with a target audience of children at an age when new things are easily learned to include something so useful and make it fun is praiseworthy indeed. I bet Pokémon will have established world peace within a generation.

The plot of the game runs along very similar lines to previous incarnations. In this instance, your character (you can choose to play a boy or a girl; I picked a boy and named him Alice, as I didn't like the female sprite) has just moved to the region of Hoenn and is ready and eager to start a career as a Pokémon Trainer. Pay a visit to the friendly neighbourhood Professor, who gives you your starting Pokémon, and you're all set.

There's a choice of three starters: Torchic, a fiery bird, Mudkip, a water creature which resembles a four-legged tadpole, and Treecko, a cool-looking reptile. Pokémon have strengths and weaknesses according to their type - Fire Pokémon are hit hard by Water attacks, for instance - so choose carefully. I'd recommend Mudkip, for reasons that will become clear later.

With your new buddy safely ensconced in a Pokéball, you set off into the world. Hoenn consists of forest and grassland, with pretty little towns at intervals, and is surrounded by sea. It's a large map to explore, and it will be a while before all areas are open to you.

Your mission is to capture other Pokémon in the wild and add them to your team, which can hold a maximum of six. Surplus Pokémon are stored on your personal computer and can be swapped in as desired at the Pokémon Center - there's a Center in every town, and you can also drop in to restore energy to tired and injured Pokémon. Once you've caught a Pokémon its data - including where it lives and how big it is in relation to your character - is sent to the Pokédex (a contraction of 'Pokémon' and 'Index', see?). Completing the Pokédex is the ultimate aim of the game, but there is much, much more to do.

On your quest you'll fight with other trainers you meet. These come in various guises; there are Sailors, Swimmers, Bug Catchers, Young Couples, Parasol Ladies and many more. Each utters a challenge or a pearl of wisdom before the battle begins: "I like wearing shorts! They're comfy and practical!" is a typical sample.

There are also the leaders of the eight Pokémon Gyms scattered across the country. Gym Leaders are strong trainers who specialise in a certain type of Pokémon, for instance Fighting or Electric. They must be defeated so you can win Gym Badges, without which you can't progress through the game.

As your Pokémon fight with wild Pokémon and other trainers' pets, they gain experience. Eventually they will go up a level and their attack, defence, speed and stamina increase. Sometimes when Pokémon reach a new level they will learn a new fighting move, and many Pokémon evolve to a higher stage when a certain level is reached. Little Mudkip becomes the stronger Marshtomp and eventually the mighty Swampert. Evolved Pokémon might not look as cute as their baby form, but they're much tougher! As you acquire more Pokémon, you can start to put together a well-balanced team with creatures that complement each other and cover a wide range of attacks and skills.

Wild Pokémon appear when you walk through long grass, in caves and in the water. The aquatic varieties can be caught with a fishing-rod, or attack you when you're riding your Pokémon through the waves (which requires it to know the 'Surf' move and is great fun). When a wild Pokémon attacks, you fight back using your own Pokémon. Either defeat it, earning your Pokémon valuable experience, or weaken it until it can be caught in a Pokéball and added to your collection.

You'll also run up against Team Magma, the villains of the piece, who want to expand the land mass by shrinking the oceans. More learning by stealth here, as lessons are taught about the importance of respecting Nature. You'll need your wits and your Pokémon about you to save the day. As their name suggests, Team Magma tend to be armed with fiery Pokémon, so choosing Mudkip at the start of the game can make battling the baddies a little easier.

I must confess that although I am as enthralled as I was by first Yellow then Silver, the other two Pokémon games in my possession, I have been a little disappointed by Ruby. It doesn't seem to make full use of the better graphics and sound capabilities of the GBA; sprites and battle animations are a little more detailed, but in looks this is closer to a Game Boy Color title than the all-singing, all-dancing games being produced for the GBA. Most of the in-game tunes have been taken from previous versions. They may have been jazzed up a little, but it's rather like comparing polyphonic and old-style ringtones: yes, it sounds better, but it's still not great.

Many aspects of the game have added refinements. In previous games you were given a bicycle; now you can choose between two models. There are berries to pick which can cure various injuries inflicted on your Pokémon; once you've picked a tree's berries it dies, so you need to plant a berry in its place to ensure future supply. There's the option to battle Pokémon two-on-two, which opens up a new range of strategies as you pick pairs that will cover each other's weak spots.

Although there is little that is totally new, what there is tends to be fun and well thought out.

One big change is a new kind of Pokémon competition in which, rather than battling, the contestants use their fighting moves to prove they're Cute, Cool, Tough, Smart or Beautiful. These attributes can also be enhanced by feeding your Pokémon with Pokéblocks, made from the berries you pick along the way. Wow the audience with your display and you can win a Ribbon to pin to your prizewinner.

Every now and then you'll meet a character who asks you to answer a few questions for a TV interview, for example 'What does Pokémon mean to you?'. You answer by picking words from a list. If you should find yourself in a house with a TV set, turn it on and see your interview. This has huge potential for childish amusement, and I was delighted to find that if you link with a friend you'll see their interviews afterwards too.

If your Pokémon learns a certain move you can gain entry to secret areas in hollow trees and clumps of grass, and turn one of them into your personal den. You can decorate your hideout with items you buy in the towns -toys, balloons, plants and furniture - and it will also be added to your friends' worlds when you link up.

And, of course, there are more Pokémon.

Many old friends from the original set of 150, including Pikachu, are included, and some from Gold and Silver. But there are over a hundred new species to collect as well. A few of my favourites, as they are described in the Pokédex:

'NOSEPASS's magnetic nose is always pointed to the north. If two of these POKéMON meet, they cannot turn their faces to each other when they are close because their magnetic noses repel one another.'

'SWABLU has light and fluffy wings that are like cottony clouds. This POKéMON is not frightened of people. It lands on the heads of people and sits there like a cotton-fluff hat.'

'ELECTRIKE stores electricity in its long body hair. This POKéMON stimulates its leg muscles with electric charges. These jolts of power give its legs explosive acceleration performance.'

'SEEDOT attaches itself to a tree branch using the top of its head. It sucks moisture from the tree while hanging off the branch. The more water it drinks, the glossier this POKéMON's body becomes.'

If that's not enough there are the extremely rare Shiny Pokémon, who look identical to the regular kind but for a slightly different colour scheme. They're hard to spot, so keep your eyes peeled!

One disadvantage is that Ruby and Sapphire aren't backwards-compatible. Previous versions Gold and Silver could be connected to the original Red, Blue, Yellow games so you could transfer beloved companions to the new cartridge. I guess we'll have to wait for another Advance Pokémon game for this facility.

As with previous games, some Pokémon are unique to Ruby and some to Sapphire, so to get the set you'll need either a friend with the other game or two Game Boys, both games and no life - oh, and a link cable.

Linking also allows you to battle your friends' Pokémon. This is much more exciting than fighting a computer-generated opponent; humans are less predictable, more intelligent, and likely to have a varied team of Pokémon. It's also, of course, much more satisfying when you win - and you'll hear stronger language than you get from onscreen characters. The drawback is long pauses while data transfers between Game Boys.

If you're in a more peaceable mood you can enter a beauty contest against your friends, or cooperate to make Pokéblocks using the Berry Blender. This is a test of skill which involves pressing the A button when a revolving indicator passes your spot on the screen. The more accurate you are the faster the needle spins, and the better quality the Pokéblock you make will be.

Progress through the game is far from linear. You do have set goals, but you can take as long as you like to complete them and travel around the region in any direction you wish, although you will need a particular Gym Badge to access some sectors. It is possible to reach the 'end' of the game by defeating all your opponents, but you can carry on playing to fill up your Pokédex and train your Pokémon to the highest possible level. To become a true Pokémon Master could take you the rest of your life.

What is the secret of Pokémon's long-lasting appeal? Well, Japanese creator Satoshi Tajiri based the game on his childhood love of exploring under rocks, in tall grass and in rivers looking for insects and other tiny creatures. With the growth of big cities in Japan, modern children were growing up unable to experience this pleasure, so he reproduced it in a game. If you've ever watched a child dig for worms or chase butterflies, you'll know how thrilling it is to stalk wild Illumise or Baltoy through the grasslands of Pokémon World.