The Signature Problems

The collision prompt is where the round earns its reputation, and it is not a physics exam. The scene is vivid on purpose. Two objects moving toward each other, a diagram, a question about what happens. The trap is to reach for velocity vectors and momentum math and start simulating frame by frame. Strip the story down and it is a closed-form question about when two lines cross, answered pair by pair with grade-school algebra. Model the scene in one precise sentence, decide what a collision even means, and the code is short. Rush past the modeling and you will simulate an unbounded loop that never had to run.