# Return a default CSS content related to CSS classes used in the `html` tree.
	# Could be inlined in the `.html` file of saved as a specific `.css` file.
	fun css_content: String
	do
		return """
.nitcode a { color: inherit; cursor:pointer; }
.nitcode .titled:hover { text-decoration: underline; } /* underline titles */
.nitcode .popupable:hover { text-decoration: underline; cursor:help; } /* underline titles */
.nitcode .foldable { display: block } /* for block productions*/
.nitcode .line{ display: block } /* for lines */
.nitcode .line:hover{ background-color: #FFFFE0; } /* current line */
.nitcode :target { background-color: #FFF3C2 } /* target highlight*/
/* lexical raw tokens. independent of usage or semantic: */
.nitcode .nc_c { color: gray; font-style: italic; } /* comment */
.nitcode .nc_d { color: #3D8127; font-style: italic; } /* documentation comments */
.nitcode .nc_k { font-weight: bold; } /* keyword */
.nitcode .nc_o {} /* operator */
.nitcode .nc_i {} /* standard identifier */
.nitcode .nc_t { color: #445588; font-weight: bold; } /* type/class identifier */
.nitcode .nc_a { color: #445588; font-style: italic; } /* old style attribute identifier */
.nitcode .nc_l { color: #009999; } /* char and number literal */
.nitcode .nc_s { color: #8F1546; } /* string literal */
/* syntactic token usage. added because of their position in the AST */
.nitcode .nc_ast { color: blue; } /* assert label */
.nitcode .nc_la { color: blue; } /* break/continue label */
.nitcode .nc_m { color: #445588; } /* module name */
/* syntactic groups */
.nitcode .nc_def { font-weight: bold; color: blue; } /* name used in a definition */
  .nitcode .nc_def.nc_a { color: blue; } /* name used in a attribute definition */
  .nitcode .nc_def.nc_t { color: blue; } /* name used in a class or vt definition */
.nitcode .nc_ss { color: #9E6BEB; } /* superstrings */
.nitcode .nc_cdef {} /* A whole class definition */
.nitcode .nc_pdef {} /* A whole property definition */
/* semantic token usage */
.nitcode .nc_v { font-style: italic; } /* local variable or parameter */
.nitcode .nc_vt { font-style: italic; } /* virtual type or formal type */

.nitcode .nc_error { border: 1px red solid;} /* not used */
.popover { max-width: 800px !important; }
"""
	end