Prison Architect, the new prison simulation game from Introversion (Darwinia, Uplink, DEFCON), has been hugely successful for the studio and it's only four weeks into the alpha stage.

Using a hybrid funding system which brings together the Minecraft paid alpha style and the tiered rewards of Kickstarter, Prison Architect has seen sales of 10,000 generating over $360,000 in just four weeks.

"We decided early on that we'd share our sales figures, because there's just no reason to keep this data secret, and it might help other indies with their own game launch plans," wrote Introversion's Chris Delay in a new blog. "We think the model we've used - a Paid Alpha crossed with Kickstarter style tiers is an excellent model for Indie Games right now, and these figures back that up."

"It's fair to say these sales are way beyond our expectations."

The blog post also details what's next for the alpha, principally a new Sector system, which divides the prison into self-contained areas.