Cities: Skylines [official site] has sold 250,000 copies in the 24 hours since launch, including preorders as day one sales. That’s more than any other Paradox game in the same period – Europa Universalis IV surpassed 300,000 sales around six months after release – and around a quarter of SimCity 2013’s first fortnight of sales.
Paradox are understandably pleased by the reception but they’re already looking to the future of the game. When I played it before release, Colossal Order CEO Mariina Hallikainen told me that the team already had free content lined up – features that weren’t quite ready for release, including tunnels. Support should continue for years though, as with Paradox’s grand strategy mainstays, and will come in the form of paid expansions and free patch updates.