Instead of three separate variables, you bundle them into one object. When data belongs together, put it in a class. Position, velocity, color - these are all groups waiting for classes.
Vector addition lives inside the Vector3D class, not scattered across your main function. This pattern makes code easier to read and harder to break.
If vector logic changes, you only fix one place. You learned that classes simplify your main logic. Compare juggling three sums to calling sum.add(force). The class hides complexity behind clean methods.
Your main code becomes shorter and clearer.