For some reason that we're unable to precisely pin down, we feel like Spore was a relatively unsuccessful game. The truth, as Maxis representatives will point out, is that it was actually a highly successful product - gifting EA its "strongest-ever" launch of a new IP and shifting over 2 million copies in its first three weeks on sale. It was also the single most-pirated release of 2008, notching up a total of over 1.7 million illegal downloads. In short, it was a game that a lot of people played.

Our critical opinion was that Spore was a great game, albeit one that failed to completely match its own ludicrous ambition. Its depiction of evolution was a bit weird, most of its five game stages were a bit shallow, and if you played as an aggressive race then half of the galaxy ended up trying to kill you. Yet despite these flaws, there was a peculiarly addictive experience sitting in-between the various pros and cons. And now Maxis is offering the inevitable expansion pack, under the title "Galactic Adventures".

As this name suggests, the new material relates entirely to Spore's Space Stage - the final and largest section of the game, the bit where your custom-evolved race gets to explore and conquer the universe. Would it have been smarter to focus on the earlier stages, the bits that arguably needed a bit more fleshing out? It's hard to say for sure. A Maxis developer told us that the company was originally working on a different pack, one set earlier in the genetic timeline. There's still a chance this material may see the light of day, but for the time being we're stuck in outer space.

On the plus side, this means we'll be getting more material from the most detailed part of the game. Or to be more precise, we'll be making more material ourselves - because the main attraction in Galactic Adventures is building your own missions. That's right kids: we're back in the land of LittleBigNuts n' Spore, Gaming 2.0. Given that building your own creatures, tanks, and genital-shaped houses was one of the most fun bits of the original game, that's neither a surprise nor a cause for concern.

The first new element to be added is a planet editor. Up until now, all of Spore's space missions have been conducted from the safety of your spaceship - "Fly to planet Clarkykat and abduct 10 cows" - but soon you'll be able to get out and walk around on foot (or on tentacle, if that's how you evolved). Since this is now the case, it's clearly important that you can design what will essentially be your game-worlds. You can raise or lower the terrain, change the global temperature and edit the water levels - and you can also place any of the thousand vehicles, creatures and other things that people have made and uploaded to the Sporepedia. So far, so good.

Things get complicated with the creation and editing of missions - despite the fact that it looks as though Maxis is trying to keep things as close as possible to the accessible-for-all approach of the existing content tools. You'll start out by choosing a cast of "actors" for your adventure - the creatures who will appear within a given quest - then move onto laying out your beasties around the play area. You can set the health of each actor, edit their default behaviour to make them aggressive or friendly, and give them pick-ups to carry. You can also give movement-based orders to your actors, perhaps telling them to patrol a certain route or to track and eat other species of your choice. You can also edit the creature's awareness radius, the distance at which it will notice the player. In typical Spore style, this is demonstrated via a simple on-screen circle - a neat way of illustrating what might otherwise be a complicated concept.

Once you're satisfied with laying out a few things, you can move on to the task of constructing a mission. Each adventure is comprised of up to five acts, each of which requires the completion of specific goals. Your actors can then be labelled with goal tags, conditions that determine how the player must interact with them to advance to the next stage of the mission. The "talk to" goal can be used to have characters dish out briefings or dialogue using text boxes, while the "posse" goal will allow the player to recruit the target creature to their party. By using modifying commands like "and" and "or", you'll be able to chain or offer a choice of actions, allowing for more complicated objectives.

In the example we were shown, the player visits a castle where he is informed about a missing princess. He then heads over to a nearby cave, where a large dragon is keeping the wench captive. Our demonstrator hadn't fully edited his mission, but in a complete scenario you might task the player with killing the beast and then returning the captive to her home. Or perhaps you might reveal that the princess was actually the one who kidnapped the dragon. Or perhaps the two of them fell in love and are now eloping - it's up to you.

In addition to the new editing tools, Maxis has also created 32 accessories for your adventurers to use, ranging from ray-guns to jump-packs. You can't create these items from scratch, but you can edit their shape in the same manner as the decorations you put on vehicles - and because these weapons actually do things, you can also adjust their power and rate of fire. All in all, it looks like the new Space Adventures will play a bit like Spore's existing Creature stage, only with a more varied selection of tasks. Once the pack is installed, quests from other users will start to appear in your game world, slotting alongside the spaceship-confined tasks that we're all used to by now.

Given that the creative aspects of Spore were always the best bits, there's no reason why Galactic Adventures shouldn't be a decent add-on. The basic tools are relatively simple, but with effort we can see how imaginative players might come up with something quite fun. As with any of these user-generated tools, the quality of the resultant gameplay will be determined entirely by the enthusiasm and ability of the user community. Given how many people have the game, we're sure there will be at least a few people out there who start pumping out original ideas - assuming the tools work as well as they should. It's unlikely that Galactic Adventures will revolutionise Spore or add anything massively deep, but if it injects a new breath of life into the franchise then we're all for it.

Spore: Galactic Adventures will be released on PC later this year.