Highlights

Highlights are ken’s way of adding visual overlays to text,[^1] much as markers or colored pencils can mark up paper documents. Highlights may be used for scholarly analysis, feedback, or meta commentary.

{ [1]: Conceptually, ken highlights resemble a <span> in HTML; the goal is to paint a region of text with additional semantics. However, the correspondence is not perfect. As their name implies, ken highlights are always intended to create a visual effect; HTML <span> tags may have a non-visual purpose. }

Highlights can be added to a ken document by original authors and by subsequent readers. Highlights are organized into layers, and individual layers can be shown or hidden.

Highlights are visualized with subtle color and lines, and exhibit helpful behaviors on mouse-over and click events. This allows semantic richness without overwhelming the text itself. However, it introduces a challenge: in modern browsers and editors, color and layout are influenced by many external factors such as light/dark theme, accessibility settings, and screen resolution. Therefore, the creator of a highlight gives only hints about its appearance (e.g., a base color and style); exact rendering is reserved for code that tweaks alpha channel and other characteristics to suit the circumstances.

effect	rendering	syntax
marker highlight	Apply a background color to text; intensify the color on hover.	[~ marked text] for default orange (#ffa500). Colors can also be specified after tilde: [~red highlighted text] or [~808 purple-highlighted text] or [~ffff00 yellow-highlighted text] or [~coral highlighted text].
box highlight	A lightly visible (mostly transparent) bounding rectangle is drawn. Color of the rectangle, and all other rectangles with the same appearance, intensifies on hover.	[| boxed text] for gray. Colors can also be specified after pipe: [|blue text] or [|e93 text] (for orange)
underline highlight	A lightly visible (mostly transparent) underline is drawn; this is different from a simple html <u> in that the underline does not get its color from the text. Color of the underline, and all other underlines with the same appearance, intensifies on hover.	[_ underlined text] for gray. Colors can also be specified after pipe: [_blue text] or [_e93 text] (for orange)
placeholder highlight	A dotted box, lightly shaded, is created to show that something is missing.