OpenTTD

OpenTTD is a classic transport tycoon sim where you build rail, roads, and airports, then stitch together profitable routes to grow bustling cities. Play online with others or go solo against computer opponents, optimize networks and timetables, and manage your empire from pocket to megacity. Mobile friendly touches like two finger map scrolling and draggable dialogs keep the interface snappy, and the whole thing is open source, perfect for tycoons who also love tinkering.