You can try this in index.css, line 976. I don't know that 'inline-block' breaks anything anywhere else but using 'inline' only will break some stuff.
/* Level 1 Menu bar: link or button. */
.linklevel1 {
display: inline-block; /* was block */
padding: 0 0.6em;
white-space: nowrap;
}
ETA: hmmmm .... very bad idea. I did not catch that the menu highlights will be be shortened. Dummy me.