A good JavaFX abacus assignment for students should have the following characteristics:
Clear instructions: The assignment should provide clear and detailed instructions on what is expected of the students, including the specific programming concepts and techniques that they are expected to use.
Well-defined goals: The assignment should have well-defined goals that are aligned with the learning objectives of the course, such as designing a functional abacus, learning about user interface design and event handling or using the JavaFX library effectively.
Challenging but achievable: The assignment should be challenging enough to push students to learn and improve, but not so difficult that it becomes overwhelming or impossible to complete.