Ships
Imagine you are a submarine and there is an enemy submarine, firing a torpedo at 1:34. You have the location of both of your submarines, as well as the direction vector of both torpedoes.
You need to have your torpedo intercept the enemy's torpedo, by firing your torpedo at a given time. Calculate how much of a delay you need (after 1:34) to correctly intercept the torpedo.
Type in the delay, and push Fire!, to see if you were correct.