hierarchy
Source sans pro Bold with all uppercase for Headlines
Source sans pro Regular for body text
Source sans pro Regular with underline for body text
“Source sans pro Light Italic for citation”
Legibility
All text should be legible and meet accessibility standards. AA level requires a 4.5:1 color contrast between text and background for normal text, and 3:1 to large text. Black text is recommended for using on light backgrounds, and white text is recommened for using on dark backgrounds.
Paragraph spacing
Keep paragraph space in the range between 0.75x and 1.25x of the type size. Keep each paragraph short to encourage viewer to read or skim through.
For example, type size 20sp, line-height 30dp, paragraph spacing 28dp.
Line length
Line lengths for body text are usually between 40 to 60 characters. In areas with wider line lengths, such as desktop, longer lines that contain up to 120 characters will need an increased livne height from 20sp to 24sp