Various types of text in Constellation apps can differ in their default font size depending on their purpose. Text used for headings are typically larger than plain body text, ranging in size depending on the specified heading level. Meta data text, which usually appear within the context of an operator's worklist or active assignment, is slightly smaller than plain body text. 

Pega specifies a default font size for each type of text that can be displayed in the end user portal. The way the font sizes are computed makes use of different techniques to ensure that size consistently remains readable and responsive depending on various viewport sizes. 

The first way this is done is by using the CSS max() function to ensure that font sizes will never fall below a specified threshold. This function accepts any number of CSS values as parameters and will return the largest value from the list. As an example, if font size were to be dictated by the following style, max(11px, 12px), the function would return 12px. For text in Constellation applications, the smallest possible font size allowed is 12px, usually reserved for meta data text.

The second part involves using the rem unit of measure in font size calculation. rem is a relative unit of measurement that is based on the font size of the root element of the document or current page. The benefits of using rem is that the font size will scale and adjust in response to various user preferences such as zoom levels and browser-defined font sizes. For supporting users with various levels of sighted ability, the adaptability of using rem ensures that the font size of text adjusts to their needs accordingly. 

Combining these two techniques for font size allows text to not only scale responsively depending on the device size and settings, but also ensure that font size never goes below a specified minimum threshold for better readability and contrast with background colors. So in the example below, font-size is determined by the higher value between either 0.875rem, or 12px. Since the computed pixel size of the rem value is the larger of the two values, the end result is text with a font size of 14px.