Planet Coaster is a Roller Coaster Management game and, quite honestly, the best one I've played! There's lots of options for pre-made coasters and has an extensive coaster editor that you can do whatever you want! I made my coaster go underground for a bit but my park attendants didn't really like that. (Too bad for them because the Roller Coaster was awesome!)
The UI is not by any means simple. This is a complex game and the UI needs to help the user understand what is going on. There's a lot of stuff going on at the same time and the UI tells the user to seek out the information they want. If you want to know how to better spend your money or find out why people in a certain area are unhappy, it's your job to investigate through data charts and user scenarios. Planet Coaster does a fantastic job of using colors to indicate status of text and graphs. The UI is also extremely visual in style which helps with taking it in one piece at a time.