Are you serious? It's one of the best NES games. Holds up better than most.

You ride around in a tank in a side-scrolling, Metroid-y ation area. You can upgrade the tank with all kinds of shit.

You can also disembark to climb around on ladders. If you find a doorway, you can enter it, where you enter a top-down Zelda-y viewpoint. This is where you fight big ass bosses.

There was a GBC remake (or sequel?), and a Genesis sequel I only know about because of Wikipedia.