Unofficial modifications expand the game even more. It may be buildings (you can now build an airport of your own design), natural phenomena, development scenarios (“green” city), and so on. Each of these expansions adds new elements to the virtual world. Instead of releasing a new series, the creators of Cities: Skylines preferred an approach with gradual modification of the original game, releasing official expansion packs about every six months. Cities: Skylines was released in 2015 - quite a long time ago by standards of the ever-changing online world, but fans are unlikely to be scared by this. Cities: Skylines is a competitor and in some ways a successor to the famous SimCity series from the 1990s and 2000s, whose history (so far) ended with a failed release in 2013.
