This was a Nintendo game very similar to Super Mario Brothers. It had the same graphics, the same basic layout (4 levels per world, 8 worlds in the game (sorta), etc.) But it was much harder. It was supposed to be the sequel to Super Mario Brothers, but was only released as Super Mario Brothers 2 in Japan. In America, we got a mutated version of Doki Doki Panic, since they supposedly thought that (according to other writeups) The Lost Levels were too hard for Americans. They can get it as part of Super Mario All-Stars, though.
Anyway, this game differs from the original SMB in the following ways:
I only played this game when it came out with Super Mario All-Stars. In that version of it, you could start over at the beginning of the last level you made it to, which made the game much easier.
World 8-4 is much like 8-4 of the original Super Mario Brothers. You have to go through a series of rooms, and in each one choose the correct pipe to go on to the next one. In this one, however, there are more lava pits, paranha plants, flying fish, and tricky jumps. It also features one of those places where you have to go on the right side of certain blocks before the area will stop looping.
After you beat World 8, there is a world 9, which is just completely screwy (underwater cloud guys and flagpoles, orange castle in level 3 with sky background, etc), but extremely easy to get through. I don't know what's up with this world. It's just completely random (note: Actually, I think this was just a bug in my savegame or something. I haven't been able to get back to world 9 again). Then
there are 4 more worlds: A-D. When I played them, they didn't seem much harder than the rest of the game. It seemed to me as if the level designer had a few more ideas he wanted to implement and so made a few more worlds to use them. There's nothing too spectacular, though, and the last level isn't nearly as hard as 8-4.