Three years ago my good friend Henning sent me a game via Amazon. For weeks I played it. Then months. And now years.

Some games stick with you like that. Games of true complexity that demand co-operation and grow with time.

Sins of a Solar Empire is just such a game. It covers culture, trade, diplomacy, economics and empire building. And big explosions. Lots and lots of big explosions.

The essence of Sins is resource management in a Real Time Strategy (RTS) game, as you carve out your galactic empire with warfleets of frigates, cruisers, capital ships and, eventually, starbases and titans – how I love titans.

Titans are your reward for surviving long enough in Sins. They come in the form of giant rail guns that fly around killing enemy capital ships with a single shot, or as huge alien superstructures that eat whole fleets with a single gulp.

But it’s not just about the big ships and big explosions. There’s diplomacy between empires as you gain trust over time and share technology. There’s trade and development to manage as you seek to balance your economy between civilian, military and science investments.

At times there are no good choices, no easy priorities, only juggling the contradictions of policy, economics and warfare in real-time crisis. Political gaming geeks will relish the headache-inducing trade-offs incumbent in every rapid-fire click of the mouse.

Thank heavens, then, that the user interface is genius simple: scroll in with your mouse to see a fighter squadron being launched or a trade port being built; scroll out a little to see your capital ship moving out of planetary orbit; further out to the enemy closing in; and further out still to the system, the stars, the galaxy, that is the contest.

The game is very Clausewitzian: destroying the enemy forces in the field rather than capturing their capital is what delivers victory. But there’s no left/right politics here: just destroy their forces with yours through decisive battle. It could be you against one rival or you and half a dozen mates versus an enemy team of 7 human players or even 7 computer-controlled empires.

For Sins’ other great virtue is the demands it makes of its players in terms of co-operation. Sins has no single player campaign mode. Sure, you can skirmish solo – but to embrace its awesome depth properly, team play is the way to go. For once, the computer AI is up to the task, such that the limited amount of “Stupid Harvester Syndrome” (a Dune 2 reference to computer managed units driving over sandworms to their certain doom) will come as a pleasant surprise to hardcore RTS gamers. But if you’re after a quick and mindless foray into gaming rather than a minimum of 4-6hrs a session, Sins is not for you.

So weekends still find me and Henning and many more of our friends screaming over a massive Skype conference call: “Hurry with the reinforcements! Finish the trade route! Where’s my Titan?!”

This is a game that embraces complexity, rewards co-operation and delivers galactic space battles of truly satisfying scale and grandeur.

Just make sure “locked teams” is on so one of your mate’s doesn’t stab you in the back.