Launch rockets at biters (and probably at your own base defense) [I don't plan on updating this to 2.0, since Space Age now has its own rocket turrets.]
Mods introducing new content into the game.
New ways to deal with enemies, be it attack or defense.
grey is worst but which is the highest tier
Green, obviously.
(Joking aside, the color palette is taken from Bob's, as for example the belts add a fourth violet and a fifth green tier.)