Tonight’s Illustrator how-to: drawing symmetrically.

Draw a big rectangle, centered where you want the center of rotation to be. Far bigger than you anticipate ever drawing in. Like ‘3x as wide as the entire canvas’ big. Give it no stroke and no fill; it’ll become invisible when it’s not selected. Layers panel: click on the dot to the right of the name of the layer. effect>distort and transform>transform in the angle box, type 360/x; in the copies box, type x-1 (where ‘x’ is however many copies of the stuff you draw you want to see – for instance if you wanted to see 15 total copies of your stuff it’d be 360/15 and 14. Illustrator can do simple math in all its numeric input boxes!) effect>distort and transform>transform – yes, a second one, this time check ‘reflect X’, make one copy, and leave everything else alone. maybe open up the layer and lock the invisible rectangle so you don’t select it by accident while moving stuff around. hit up the appearance palette’s dropdown menu, ‘clear appearance’ start drawing shapes if you want to edit the symmetry, then click on the dot you clicked in step 2, then go to the appearance palette and click on the ‘transform’ entry.

If at some point you want to tweak individual instances of your symmetric stuff, then click on the dot next to the layer’s name and do object>expand appearance. If ‘expand appearance’ is ghosted then go unlock the invisible rectangle you drew in step 1.

You could also go pay money for Astute Graphics’ MirrorMe plugin, but that tends to not play well with wanting to have symmetry happening across multiple layers, plus I can never remember how to use the damn thing because they only provide documentation in the form of frickin’ youtube videos. This way is covered by what’s already part of AI, and you can do stuff like have, oh, 14 copies of what you draw on one layer, and 11 on another, and expect that to stay consistent across closing and re-opening the file.