The letter A above consists of many Sierpinski triangles, blank spaces of which are colored black. Using of triangular grid to form letter gives some Gothic effect. Font designer Frodo7 created a font Sierpinski Black using such principle, which consist of 87 characters inluding Latin capital and lower letters and numbers. A sample pattern of the font is represented below. Artist created several variations of this font with different kinds of filling of letters.
Frodo7 also created another font based on fractal Fractal font, where letters look like wide tape, which curl into form of lowercase letters. Letters are filled with fractal pattern of black and white rectangles. Sample letters and fractal pattern, which is used for filling letter, are represented below.
Another fractal font was created by Tony de Marco. It is based on simple raster font, where letters are divided into pixels. Every pixel is separate fractal of regular located circles.
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If you know another fonts based on fractals, please let me know, I will happy to update this post.