bones starter theme menu

hi,
im trying to modify style.css of bones wordpress starter theme
( https://github.com/eddiemachado/bones/blob/master/library/css/style.css )

my question is, i want to make a menu look like the following
http://buildinternet.com/project/supersized/slideshow/3.2/demo.html (upper left corner)
i’ve look at the CSS and found:

ul#demo-block{ margin:0 15px 15px 15px; }
ul#demo-block li{ margin:0 0 10px 0; padding:10px; display:inline; float:left; clear:both; color:#aaa; background:url('img/bg-black.png'); font:11px Helvetica, Arial, sans-serif; }
ul#demo-block li a{ color:#eee; font-weight:bold; }

i don’t want to make buggy/crappy CSS, so what should i add to style.css to make a menu look like something in the following example above(black img background n transparent)?