Dotsies is a font designed by Craig Muth in 2012 that only consists of square dots. Each letter of the Latin alphabet is a column of at most five such dots, and words become pixel patterns.
The font is designed to be space-efficient, easy to type with one hand, and to allow quick pattern recognition of common words.
The homepage, dotsies.org contains a nice "tutorial" text, which gradually transitions from Dotsie-arranged Latin characters to pure Dotsies font.