You, as cool dude Nova, must mount your attack on the six various areas of the city. Once you've secured them, its off to the final base. The six levels are actually have a bit of an adventure element. See, before you can get to the boss of each level, you need to find a contact that will give you a key card. Then you can advance.
Some levels require plenty of exploration while some are fairly linear.
There's also a few small paths that deviate from the main course, leading to power-ups and goodies. It can be a bit annoying to go through so much of a level after you die, but it's still tolerable. However, you are forced to start the level over with a crappy boomerang if you lose all lives. Passwords are provided, but the game can be beaten in an hour or two, so these aren't really necessary. The power blade mentioned in the title is Nova's boomerang, the main weapon of the game.