udlepsprog2/prog2-lib ? reverse-engineered prompt

Build me a small Java library for the Programació 2 course at UdL that gives students a simple set of utilities for basic graphics, a few geometry helpers, and some other small classroom friendly tools.

I want it to feel like a lightweight, easy to read reimplementation of a tiny part of the old ACM Java libraries, not a full clone. Keep the API simple and practical for teaching, with clear classes and methods that are easy for beginners to use in exercises and examples. Please make sure it builds cleanly with Gradle and include tests for the main behavior. If you need to check anything current or unclear, look up the relevant docs online and keep the design minimal and educational.