add "operator" span class
add jquery & initial correspondence.js
css hover class & jquery
unhover
persistent hover (only unhover when there is a new hover)
clear current hover if clicking outside of other objects
align equation & word equation
used "selected" instead of "hover" to describe selected element
add fullstop at end of word equation (which is not selectable)
.highlighted CSS class
structure class
set up cousins & siblings
highlighting siblings & cousins
brighter selection colour
adjust CSS
index.html