M is an old (2011) and unbelievably small (12KB) fractal viewer.
This isn't some .NET program, either, or anything where the real work is done elsewhere. It was developed in assembly language for the maximum possible efficiency.
Launch M and it displays the regular Mandelbrot set. The big limitation of the program is this only appears in a 512x512 pixel, 256-colour window.
Navigation is easy. Left-click a point on the window to zoom in; right-click to zoom out; spin the mouse wheel to select a zoom window size, move it with the mouse cursor, and left-click to select that view.
If the palette isn't giving you the best results, click Colors > Constant Subtract Shift (or Constant Add Shift) and M cycles through its colours, creating an animated effect.
Alternatively, hit + or - on the numeric keypad to shift the palette once only. Repeat until you find something you like, then save the image as a BMP file, or record the coordinates for revisiting later.
M's low image resolution makes it a weak fractal viewer, but the program's tiny size gives it some curiosity value. We've probably never seen a 12KB stand-alone program which does so much.