This is my first-started Qt5 program. It shows numbers from 0 to 1000 in any of several shapes (which are available depends on the number, e.g. 91 is composite, centered hexagonal, and triangular). It's inspired by Doman's flash cards, but goes beyond number sense to teach kinds of numbers, such as square numbers. Here's a screenshot showing 144 as a Fibonacci number:
The program still has debugging code in it, and I'm not sure what features I should add before releasing version 0.1.0. What do you think?