A puzzle game similar to Tetris , Dr. Mario features Nintendo mascot Mario as a doctor. Play consists of dropping two-sided vitamin capsules into an eight-block-by-16-block playing field populated by viruses of three colors (red, yellow, and blue).
There are six types of capsules, differentiated by their color: red-red, yellow-yellow, blue-blue, red-blue, red-yellow, and blue-yellow. The player must rotate and position these capsules on top of and alongside the viruses and other capsules in an effort to eliminate the viruses. Both viruses and capsules are eliminated when four or more objects of corresponding color are placed in a row or column. A player completes a level by eliminating all viruses on the playing field. Conversely, the game will end if any capsules obstruct the bottle's narrow neck at the top row of the field. The game consists of 21 distinct levels, whose starting virus counts range from four at level 0 to 84 at levels 20 and higher. Above level 20, each level starts with 84 viruses. Levels do not increase in difficulty past level 20. Much like Tetris , the player may choose a level of difficulty to start, along with the game's speed and a selection of background music .
The Game Boy version of the game is nearly identical to its NES counterpart. In keeping with the technical limitations of the device, the game features a playfield measuring eight-blocks by 15-blocks and viruses of black, white, and gray.
Two player gameplay in either version consists of two side-by-side playfields that can be level-adjusted according to the strength of each player. The first player to win three games wins the match. The objective is to be the first to clear the viruses or to block the opponent's field to the top. An added element is the ability to "rain" down random blocks into the opponent's playfield by achieving double (triple, quadruple, etc.) combinations of eliminated lines on the same vitamin.