mandelbrot-viewer is a simple and interactive viewer, you can zoom in and out with + and -.
The GIF screencast is of course sped up, somehow, it looks like something has been locked and the system is tracking down the subject like in sci-fi movie.
mandelbrot-viewer is written by David Ulrich in C with ncurses under the AGPLv3, based on Ken Perlins code snippet, currently git-a3f2762 (2015-10-30).