Nougs
Whimsical, simple games - match (picture and word or picture and name), catch the microbe, word guessing and spelling, dot-to-dot (you set the dots, the macrophage connects them), maze.
The content is microbes and the immune system, and the scientists who built our understanding of the immune system.
Serendipitous learning might happen.
Macrophage art by Leith Walton.