The Introversion Humble Indie Bundle was a massive success, selling more games in two weeks than the developer had in 10 years: "It was our biggest single sale of any sale we'd ever done before, financially and in terms of player numbers, says creative director, Chris Delay. "Twice as many people play our games thanks to Humble Bundle."

But even though alternate distribution platforms can be profitable, Chris admits that landing Prison Architect on Valve's platform was the ultimate aim: "I think Steam is obviously the market leader. I definitely think that. And I would feel very frustrated if I had a game and Valve turned it down. Getting on Steam is like a number one objective for us, so we have to make sure the game is good enough.

Introversion's managing director, Mark Morris, is just as modest about their future titles: "It's a really good litmus test, If Valve aren't launching your game, you really have to ask yourself why."

"If we gave Steam a steaming pile of turd I don't think they'd put it on Steam just for old times' sake." continued Chris. The other extreme is Xbox Live Arcade which does have extremely rigid requirements for release. They won't release anything until it's totally finished, 100% bug free, matches their menu, and user interface guidelines. They've made it very hard to actually make games on there and make money, because it just takes so damn long to meet all their requirements."

The creative director praised Valve's open-door policy: "Valve are kind of like in this middle zone, which seems to work really well. They will release games that are buggy, unreliable and a little bit crashworthy, but they don't consider that to be a major drawback because it's a PC game: 'We could wait another year until it's totally polished, or we could release it.' They're kind of willing to go with that, but they're also willing to host really cutting edge indie stuff right next to big commercial stuff like Skyrim. And sometimes the indie stuff will get a bigger bang. They don't think Skyrim is more worthy of than VVVVVV."

Introversion recently annouced that Prison Architect will be entering paid alpha later on in the year. Until then, why not read Graham's Prison Architect preview ?