Maybe I'm just not clever enough, but I find the more complex Spiral Galaxies puzzles very hard to solve just within the applet. This is mainly because I'm missing a tool I tend to apply on paper: the ability to indicate that a cell is part of a certain galaxy without yet knowing the exact borders of the cell, if any.
Now, if it were possible to change the background color of cells, just like in for example, Country Roads, it would be possible to assign a color to a galaxy and mark cells you've determined to be part of that galaxy.
Strongly seconded! Considering the markup options some of the other applets have, it would be quite nice to have the feature to color a square on Spiral Galaxies.
I would like to add this at some point, but for technical reasons it requires some effort. More than zulio's request to add bars instead of crosses to the heterocut and neighbours genres. But some day...