Cities Skylines

Cities: Skylines is a building game developed by Colossial Order. The game is a single-player open-ended city building simulation. Players engage in urban planning by controlling zoning, road placement, taxation, public services and public transportation of an area. Players work to maintain various elements of the city, including the budget, health, employment and pollution levels. Players are also able to maintain the city in a sandbox mode which provides unrestricted creative freedom for the player.

Cities: Skylines is a progression of development from Colossal Order's previous Cities in Motion titles, which focused on designing effective transportation systems. While the developers felt they had the technical expertise to expand to a full city simulation game, their publisher Paradox held off on the idea, fearing the market dominance of SimCity. After the critical failure of the 2013 SimCity game, however, Paradox greenlit the title. The developer's goal was to create a game engine capable of simulating the daily routines of nearly a million unique citizens, while presenting this to the player in a simple way, allowing the player to easily understand various problems in their city's design. This includes realistic traffic congestion, and the effects of congestion on city services and districts. Since the game's release, various expansions and other DLC has been released for the game. The game also has built-in support for user-generated content.

The game was first released for the Windows, macOS, and Linux operating systems in March 2015, with ports to the Xbox One and PlayStation 4 game consoles being released in 2017 and for the Nintendo Switch in September 2018 developed by Tantalus Media. The game received favourable reviews from critics, and was a commercial success, with more than six million copies sold on all platforms as of March 2019.

Gameplay
Players start with a plot of land - equivalent to a 2-by-2-kilometre (1.2 mi × 1.2 mi) area - along with an interchange exit from a nearby highway, as well as a starting amount of in-game money. The player proceeds to add roads and residential, industrial, and commercial zones and basic services like power, water, and sewage as to encourage residents to move in and supply them with jobs.

As the city grows beyond certain population tiers, the player will unlock new city improvements including schools, fire stations, police stations, health care facilities and waste management systems, tax and governing edicts, transit, and other features to manage the city. One such feature enables the player to designate parts of their city as districts. Each district can be configured by the player to restrict the types of developments or enforce specific regulations within the district's bounds, such as only allowing for agricultural industrial sectors, offering free public transportation to residents in the district to reduce traffic, increased tax levels for high commercialized areas, or even with the Green Cities DLC, placing a toll on fossil fuel vehicles entering a district while excluding hybrid and electric vehicles, akin to the Electronic Road Pricing.

Buildings in the city have various development levels that are met by improving the local area, with higher levels providing more benefits to the city. For example, a commercial store will increase in level if nearby residents are more educated, which in turn will be able to allow more employees to be hired and increase tax revenue for the city. When the player has accumulated enough residents and money, they can purchase neighboring plots of land, allowing them to build up 8 additional parcels out of 25 within a 10-by-10-kilometre (6.2 mi × 6.2 mi) area. The parcel limitation is to allow the game to run across the widest range of personal computers, but players can use Steam Workshop modifications to open not only all of the game's standard 25-tile building area, but the entire map (81 tiles, 324 square kilometers).

The game also features a robust transportation system based on Colossal Order's previous Cities in Motion, allowing the player to plan out effective public transportation for the city to reduce traffic. Roads can be built straight or free-form and the grid used for zoning adapts to road shape; cities need not follow a grid plan. Roads of varying widths (up to major freeways) accommodate different traffic volumes, and variant road types (for example roads lined with trees) offer reduced noise pollution or increased property values in the surrounding area at an increased cost to the player. The road system can be augmented with various forms of public transportation such as buses and subway systems.

Modding, via the addition of user-generated content such as buildings or vehicles, is supported in Skylines through the Steam Workshop. The creation of an active content-generating community was stated as an explicit design goal. The game includes several premade terrains to build on, and also includes a map editor to allow users to create their own maps, including the use of real world geographic features. Mods are also available to affect core gameplay elements; prepackaged mods include the ability to bypass the aforementioned population tier unlock system, unlimited funds, and a higher difficulty setting.

Development
Finnish developer Colossal Order, a thirteen-person studio at the time Cities: Skylines was released, had established its reputation for the Cities in Motion series, which primarily dealt with constructing transportation systems in pre-defined cities. They wanted to move from this into a larger city simulation like the SimCity franchise, and in preparation, developed Cities in Motion 2 using the Unity game engine to assure they had the capability to develop this larger effort. They pitched their ideas to their publisher, Paradox Interactive, but these initial pitches were focused on a political angle of managing a city rather than planning of it; the player would have been mayor of the city and set edicts and regulations to help their city grow. Paradox felt that these ideas did not present a strong enough case as to go up against the well-established SimCity, and had Colossal Order revise their approach.

The situation changed when the 2013 version of SimCity was released, and was critically panned due to several issues. Having gone back and forth with Colossal Order on the city simulation idea, Paradox used the market opportunity to green light the development of Cities: Skylines.

One goal of the game was to successfully simulate a city with up to a million residents. To help achieve this goal, the creators decided to simulate citizens navigating the city's roads and transit systems, to make the effects of road design and transit congestion a factor in city design. In this, they found that the growth and success of a city was fundamentally tied to how well the road system was laid out. Colossal Order had already been aware of the importance of road systems from Cities in Motion, and felt that the visual indication of traffic and traffic congestion was an easy-to-comprehend sign of larger problems in a city's design.

To represent traffic, Colossal Order developed a complex system that would determine the fastest route available for a simulated person going to and from work or other points of interest, taking into account available roads and public transit systems nearby. This simulated person would not swerve from their predetermined path unless the route was changed mid-transit, in which case they would be teleported back to their origin instead of calculating a new path from their current location. If the journey required the person to drive, a system of seven rules regulated their behavior in traffic and how this was shown to the user, such as skipping some rules in locations of the simulation that had little impact while the player was not looking at those locations. This was done to avoid cascading traffic problems if the player adjusted the road system in real time. The city's user-designed transportation system creates a node-based graph used to determine these fastest paths and identifies intersections for these nodes. The system then simulates the movement of individuals on the roads and transit systems, accounting for other traffic on the road and basic physics (such as speed along slopes and the need for vehicles to slow down on tight curves), in order to accurately model traffic jams created by the layout and geography of the system. The developers found that their model accurately demonstrates the efficiency, or lack thereof, of some modern roadway intersections, such as the single-point urban interchange or the diverging diamond interchange.

Release
Cities: Skylines was announced by publisher Paradox Interactive on 14 August 2014 at Gamescom. The announcement trailer emphasized that players could "build [their] dream city," "mod and share online" and "play offline"—the third feature was interpreted by journalists as a jab at SimCity, which initially required an Internet connection during play. Skylines uses an adapted Unity engine with official support for modification. The game was released on 10 March 2015, with Colossal Order committed to continuing to support the game after release.

Tantalus Media assisted Paradox in porting the game to the Xbox One console and for Windows 10, which was released on 21 April 2017. This version includes the After Dark expansion bundled with the game, and supports downloadable content up to the "Industries" expansion, but not including the "Concerts" expansion. Tantalus also ported the game and the After Dark expansion for PlayStation 4, released on 15 August 2017. Both Xbox One and PlayStation 4 versions received physical release versions distributed by Koch Media. Tantalus also ported the game for the Nintendo Switch, which was released on 13 September 2018 and included the "After Dark" and "Snowfall" expansions.

The game was built from the ground-up to be friendly to player-created modifications, interfacing with Steam Workshop. Colossal Order found that with Cities in Motion, players had quickly begun to modify the game and expand on it. They wanted to encourage that behavior in Cities: Skylines, as they recognized that modding ability was important to players and would not devalue the game. Within a month of the game's release, over 20,000 assets had been created in the Workshop, including modifications that enabled a first-person mode and a flying simulator. As of March 2017, over 100,000 user-created items were available. Many of these fans have been able to use crowd-funding services like Patreon to fund their creation efforts. Paradox, recognizing fan-supported mods, started to engage with some of the modders to create official content packs for the game starting in 2016. The first of these was a new set of art deco-inspired buildings created by Matt Crux. Crux received a portion of the sales of the content from Paradox.

An educational version of Cities: Skylines was developed by Colossal Order and the group TeacherGaming and released in May 2018. This version includes tutorials and scenarios designed for use in a classroom, as well as a means for teachers to track a student's progress.

Expansion packs
Cities: Skylines offers several DLC expansion packs. Below is a list of major expansion packs provided by the developers. All DLC is developed for the Windows versions first, while release for console versions tends to follow some months later.