## Context DEF CON badges often hide secrets or puzzles, and printing into very small text can support this feature. ## Problem The only manufacturing layers with printing resolution high enough to form text at 0.5mm height are the metal layers, namely copper and gold. ## Solution Place small text in metal layers. ## Process It's quite difficult to print text into a copper trace, so we developed a hack to do this. This works only on Gerber RS-274X formats, previous versions require a different set (**\%IPPOS\*%** or **\%IPNEG\*%**) of primitives. 1. Layout items in an unused blank layer 1. Open its Gerber file in a text editor 1. Add this data to the end of the F_Cu layer 1. Change the preceding **\%LPD\*%** to **\%LPC\*%** for subtraction 1. Repeat for F_Mask or whatever other metal layer exists ## Warning While the _gerber_combine(1)_ script from [KiCad Utils](https://www.github.com/bobc/kicad-utils/) executes without errors even after **eight years** of project convalescence, it seems to produce **flawed output.** If you look carefully there will be a lot of **missing pads** in the generated Gerber file produced by subtracting layers. ``` user@host:~/projets/kicadutils$ python3 scripts/gerber_combine/gerber_combine.py circraftzero-F_Cu.gbr -s circraftzero-User_1.gbr -o circraftzero-User_2.gbr user@host:~/projets/kicadutils$ python3 scripts/gerber_combine/gerber_combine.py circraftzero-F_Mask.gbr -s circraftzero-User_1.gbr -o circraftzero-User_3.gbr ```