Note: this is an excerpt from the instruction booklet.
Once upon a time, there was a peaceful world called Sarasaland. In this world there were 4 kingdoms named Birabuto, Muda, Easton, and Chai. One day, the skies of Sarasaland were suddenly covered by a huge black cloud. From a crack in this cloud, the unknown space monster Tatanga emerged to try to conquer Sarasaland. Tatanga hypnotized the people of all the kingdoms so that he could control them in any way he liked. In this way he took over Sarasaland. Now, he wants to marry Princess Daisy of Sarasaland and make her his queen. Mario came to know these events, and has started on a journey to the Chai Kingdom where Princess Daisy is held captive, in order to restore peace to Sarasaland. Can Mario defeat Tatanga, release the people from his insterstellar hypnosis, and resuce Princess Daisy? It's all up to you and Mario's skill. Go for it Mario!!
At last, a new game series for our plumber hero. Placing him in the previously unknown world of Sarasaland, Mario has to trek through 12 enemy-ridden levels to save the Princess Daisy. Why this game deviated from the original themes I don't know, but it's nice to have something new for a change.
Giving credit where credit is due, this was the first Game Boy game. Automatic respect, just like the Super Mario Bros, World, and SM64 games. The graphics were smooth, but the characters are tiny, so sometimes it's hard to see them. The sound affects were standard Mario fair, featuring the stomps, whomps, smashes, crashes, bashes, cracks, and bursts that we've come to know. The music is all good and fine, although slightly repetitve. The Gameplay is similar to the other Mario games of the genre, which stayed similar right up until the 3D era. So you're just traveling, level by level, to the boss stage to rescue the Princess. However, this is notably the first game in which Mario used vehicles, the plane and the sub, to reach his goal.
This is definetly one of the greatest Game Boy games, and still stands the test of time. It will undoubtedly go right to the end with the Game Boy itself.