OpenTTD - An open-source clone of the classic game ...
Thunkable - Powerful but easy to use, drag-and-drop mobile app builder.
Simutrans - Simutrans is an open-source transport simulator.
MIT App Inventor - App Inventor is a cloud-based tool, which means you can create apps for phones or tablets right in your web browser.
Transport Tycoon Deluxe - Transport Tycoon Deluxe is a Business Simulation developed by Chris Sawyer and published by MicroProse.
Bubble.io - Building tech is slow and expensive. Bubble is the most powerful no-code platform for creating digital products.