This is a terrible article. In the first subplot, there is no explanation of what v(b1) and v(c2) are. The -8 on the on y axis (amplitude) looks like an upside down 8.

Further down there is a sentence: "First, the Fuzz Face is a two-transistor feedback amplifier that turns a gentle sinusoid signal into an almost binary “fuzzy” output." But the figure does not match this - there is no "gentle sinusoid" wave shown on the first fuzz face plot.