Improves on every aspect of the original, and though it's more difficult it's a lot less frustrating due to the overall better design. It's not without its faults though; there's still a couple of difficulty spikes (7--2 is a nightmare), and there are still a few questionable design choices, like sending you back to the beginning of the stage after dying to the final boss and not replenishing your health between the final boss stages. Still a damn good game, and one of the best on the NES.