Scroll a text box up and down using arrow keys, mouse on a scroll bar or dragging and dropping the text itself. The code automatically estimates the total length of the text so the scroll bar is updated when the text is moved by other means. Press spacebar to continue appears once the text has been scrolled to the bottom. I use a new jitter method to update otherwise static components to keep them in front of the scrolling text.
It works better online because the arrow keys can be continually pressed.