Originally this was a software exercise. The software simulator for Train Thing is written in PHP [1] to execute the simulator logic and generate the HTML [2] to display the dynamic results using a web browser. Locally on my PC/Laptop the XAMPP/Apache [3] server was used to process the PHP code and deliver the HTML and graphics to the browser. I use the Mozilla Firefox browser, but any major browser works (Edge).

When the exercise became a project additional development tools were needed. To organize documentation and comments about the project more tools. Two TechSmith video tools are used to edit screen shots and videos for documentation and help.

1 At one time PHP, a server-side scripting language, stood for "Personal Home Page" but now stands for the recursive acronym "PHP Hypertext Preprocessor."

2 HTML just stands for "HyperText Markup Language." 

3 XAMPP is a free and open-source cross-platform web server solution stack package developed by Apache Friends, consisting mainly of the Apache HTTP Server, MariaDB database, and interpreters for scripts written in the PHP programming languages.