As is the case with most Game & Watch games, there is only one level now and it's kind of like a combination of the first and last levels of the original game. You use ladders to climb up onto girders and have to avoid rolling barrels as you do so. Eventually you get to the top where you have to turn on a crane with a switch and swing on its hook in order to sever the cables which are keeping up the platform that Donkey Kong is standing on. So many aspects of the original game are lost, which is a shame. On the other hand, however, this one level is now much more detailed; rather than just looking like girders in a black void (as it originally did) the events of the game now very clearly take place on a construction site and you can even see the skyline of a city in the background.
But while the level itself may look nicer, all of the characters look very weird (even in the box art, as you can see!). Mario looks like a generic Game & Watch man, Donkey Kong looks has a very weird face and Pauline (who is actually part of the background) is just a really bad doodle of a woman. The gameplay is also much jerkier and unnatural, making it often hard to time things, but then all of these things are to be expected of any Game & Watch title due to the limitations.
Once you've beaten Donkey Kong, you can continue to play through again and again to increase your high score and I actually prefer the Game & Watch score system over the original (it's more fun), but other than this and another few minor improvements (it's quite nice to see such an old double screened game too), I think this is a game you'll only enjoy if you're a big Nintendo, Mario or Donkey Kong fan.