Thanks very much! I did originally implement enemy lifebars, but I felt they cluttered the screen too much. I suppose I could have just shown one lifebar for the last enemy that you damaged.
Yes, I was thinking that, similar to how streets of rage did it. The life bar of the current/last engaged enemy appears, only one life bar at a time. In this case, I was thinking on the lower right, and not above the enemy heads. To reduce confusion and clutter, you can probably make the width of the enemy smaller too (if you decide to implement the life bar).