I like the game, but maybe some occasional life drops would be useful as it is unforgivin when you get hit. If that is the point that you are bound to die as each level gets harder, it is really good! Movement-wise, it is a bit hard to change direction and player is slow. All in all, great game!
To address the "joined together" theme, team come up with more of a story concept. Grim Reaper joins with the souls he carries and thus takes the special abilities. Furthermore, storyline should be that then Grim Reaper joins the souls to the afterlife and other passed souls. ^^