fade-in: [selector] (duration) [(display property)] [await] [every (time)] [after (time)][, (selector)...];
This command fades in an element or a set of elements from an existing opacity. It is more performant to use CSS directly (search for "CSS fade transition") for transitions, but this can be a quick and performant option when there is not a lot else going on on the page.
selector = An optional CSS selector referencing a single element (it supports me, self or this to reference the target selector it is used under) or a set of elements. If this is not specified, fading will occur on the target selector.
duration = The length of time it takes for the fade in to complete. Syntax is regular CSS duration format, eg. 1s (1 second) or 500ms (500 milliseconds).
display property = Optional. The display property (like "inline-block", "block", etc.) that the element will use when the fading in begins.
This command also supports the await option, which will pause the event flow until the fading has completed before continuing. Note that if the fade does not fully complete, then the event flow will not continue from where it left off. See the fade-to command for an example of using "await".