Fighting bosses in this game is a snap. Just remember to use your entire
desk to sweep the mouse from left to right and vice versa; dont' confine
your arm movements to your mouse pad. This way you can jump from one end
of the room to another while firing without ever having to stop and reset
the mouse position . 
You can also use the right mouse button to re-aim your weapon elsewhere 
but if you use this strategy you honestly won't need to do so.