I'm seriously relearning calculus, statistics, and linear algebra, and I'd like to reinforce the material through practical programming projects. What kinds of projects would let me apply these subjects meaningfully? Would a video game or simulation be a good choice, or are there other project ideas that combine some or all of these topics?
4 Answers
A small physics simulation would be an excellent fit. You could use calculus for position, velocity, acceleration, and numerical integration; linear algebra for vectors, rotations, and coordinate transformations; and statistics to analyze the simulation’s results or compare different methods.
Another useful project would be to build a small mathematics library from scratch. Implement functions such as sums, means, standard deviation, matrix operations, and numerical derivatives, then write tests and compare your results with established libraries. That gives you practice both applying the concepts and verifying that your implementations are correct.
Pick a problem that naturally uses one or more of the subjects and solve it in the programming language you know best. Examples include modeling a projectile, analyzing sensor data, implementing least-squares regression, or creating a particle simulation. The important part is to explain the mathematics, implement the solution yourself, and investigate how accurate the results are.
A game can definitely involve all three areas. Even a simple 2D game could use vectors for movement and collisions, matrices or coordinate transforms for graphics, calculus for motion, and statistics for things like balancing difficulty or analyzing player behavior.

You could extend that into a larger problem, such as fitting a model to data or simulating a physical system, so the library is supporting a real application rather than only isolated functions.