Hi. Forgiving me for asking what must be a rather old question, but nevertheless: what would be the simplest method for calculating whether a collision has occurred (or perhaps, will occur) between two circles that are moving at high velocities? I'm thinking in a simple video game context, where the positions of two objects are updated every few milliseconds, and the next position is based on the previous position and the current velocity, and the "body" of each object is represented by a simple radius. Obviously it is not difficult to see if a collision is occuring at any particular point in time, by checking if the circles overlap, which would be good enough for me; however, since the objects are moving so fast, it is possible that a "leap over" scenerio might occur, in which the collosion occurs in between steps and thus is not detected. It is not good, either, to simply check if their movement vectors intersect, because then it is possible for them to pass very close to each other in what should be a collision, but is not detected. (E.g., two very close, but parallel lines of movement).