It's extremely good for the time, obviously. But looking at it through a modern lens, it's actually quite frustrating.

I think it's a mixture of the slightly janky physics and the classic NES style punishment for losing. I know you can continue from the world you lost on, but it's still not got the snappy right-back-to-playing style that I've grown accustomed to.

Despite all this, it's far from the worst NES game I've played, and holds up more than it has any right to.