RollerCoaster Tycoon 3 marks the series' debut to a 3D engine, and is the first major title in the series created by a company outside Chris Sawyer Productions.
The new engine brings numerous cosmetic additions like day/night cycles; reflective water; improved terraforming tools; and guests who differ in age, gender and appearance (and who can be created by the player in the Peep Designer), while gameplay changes are even more substantial - construction can take place even when the game is paused; park staff now have happiness levels, manageable wages, and can be trained; shops and stalls have more purchasable items which can be changed so, for example, drinks are sold with ice cubes; rides can be viewed from a first-person camera from any seat within the ride; VIP guests can appear, with a secondary objective requiring to please them; fireworks can be created and combined in the MixMaster; new custom billboards can make use of image files on the player's computer, and custom stalls also added.
The main gameplay idea remains the same as in the preceding titles - the player is positioned as a manager of a theme park, and has to satisfy the goals of a particular scenario. This time, each scenario has three sets of objectives that act as a sort of difficulty setting - Apprentice, Enterpreneur, and Tycoon, all of which have to be completed in succession. The career mode puts the player in a series of scenarios, many of which are locked but can be unlocked if previously available scenarios are finished at the Apprentice level. Unlike the previous titles, RollerCoaster Tycoon 3 comes with a sandbox map by default, allowing the player to build a park using any object in the game with unlimited funds.