Mass

The earlier chapters of the book have gone into several aspects of motion: velocity, acceleration, vectors, friction, bouncing, easing, springing, and gravity. One thing that I have pretty successfully gotten away with ignoring is the concept of the mass of the object being moved around. Now, I'm going to reissue my standard disclaimer here, and say that there are probably several points in the book so far where, scientifically speaking, mass should have been in the equation. But I've generally concentrated on doing things mostly correctly, and kept the emphasis on making sure it looks right. Most important, the final result must be efficient enough that it won't totally kill Flash in the process.

Unfortunately, or maybe fortunately, I have reached a point where I just can't ignore mass any longer. Mass is just so tied up in the subject of momentum that I'm just going to have to confront it head on.