I have found another way to
waste pass time on my devices: Mini Metro. It was included in the App Store Best of 2016 and won a bunch of other awards. The principle of the game is simple: you are responsible for building a metro/underground/subway network in a major city. Mini Metro comes with 15 different cities. London, Paris, New York, and Berlin are unlocked. You gain access to other cities by achieving a passenger-carrying goal in some other city, for example, move 500 passengers on the Berlin network and Melbourne opens up. The maps reflect the layout of the water features of the city.
You start with the ability to build three different lines indicated by the coloured dots to the right. You have assets of three engines and the capability to create three tunnels. Stations appear on the map; initially, they are indicated by squares, circles, and triangles, but different shapes appear as the game progresses. To construct a line, just touch a station symbol and drag to the next station.