Good old-fashioned arcade hack-and-slash fun!
Catchy music, fluid controls, addictive gameplay.
The on-the-fly transformations are a neat idea, but in practice, not all transformations were equally desirable. After a certain point, the enemies got so powerful that it was useless to be in any form other than the "R" form.
Also, it took me a few tries to realize how to continue after dying. :)