The Analog Thing is a “high-quality, low-cost, open-source, and not-for-profit cutting-edge analog computer.” I really want it, but explaining it to me would be like explaining the concept of a dictionary to the Prince Regent.
THAT allows modeling dynamic systems with great speed, parallelism, and energy efficiency. Its use is intuitively interactive, experimental, and visual. It bridges the gap between hands-on practice and mathematical theory, integrating naturally with design and engineering practices such as speculative trial-and-error exploration and the use of scale models. Dynamic system modeling on THAT can serve a variety of valuable purposes. It may help understand what is (models of), or it may help bring about what should be (models for). It may be used to explain in educational settings, to imitate in gaming, to predict in the natural sciences, to control in engineering, or it may be pursued for the pure joy of it!
500 Euros, with discounts for educators and students.