Dystopian strategy game Frostpunk has sold three million copies in as many years.

That's according to a post on Steam, in which developer 11 Bit shared the milestone and kicked off rolled out the soundtracks for The Last Autumn and On The Edge expansion packs. These are available free of charge to anyone who bought the Season Pass.

Meanwhile, 11 Bit has kicked off a sale event to celebrate Frostpunk shifting three million copies.

"All of this wouldn't be possible without you lot," the studio wrote.

"Therefore, we'd like to celebrate the occasion and take a moment to give a heartfelt Thank You to not only Frostpunk-lovers but our whole community. That's why we've just launched a special, time-limited 11 bit studios sale."

As of the start of 2019, 11 Bit said that Frostpunk was closing in on 1.5 million copies. At the time we caught up with the company's publishing director Pawel Feldman to discuss how the title had reached this milestone.

Last year, 11 Bit committed $21 million to develop seven new games.