Invertype is a monospaced, monoheight inverted typeface intended for outdoor use. It was created in 2008-09 by Dario Dević, mentored by Nikola Djurek and Damir Bralić, at the University of Zagreb School of Design. 

Its purpose is to enable a regular person to communicate on a mass scale using as least as possible material. This way, you can plaster the city with your message using only old, once-used sheets of paper and almost no printer ink. 

Each glyph fits onto a standard sheet of paper so it can be printed easily at home with an A4 or A3 printer. The letterforms are inverted, so the amount of ink required to print them is extremely reduced. It doesn't require any knowledge of typesetting or software — it can be used at www.invertype.com by anyone with a web browser.