These prototype fonts were built by Ken Lunde and his colleagues at Adobe for developers to test support for “variable font collections” that combine the technologies for both variable fonts and font collections. The fonts simulate the structure (styles, glyphs, character mapping, features, etc) of Source Han (Serif & Sans) and Noto CJK, but only contain a dozen or so functional glyphs, repeated thousands of times. Lunde’s introduction explains how variable font collections can greatly reduce file sizes for type systems with expansive character support, like Pan-CJK fonts for typesetting East Asian scripts.