In Virus, a bonus counts down with every pill dropped, and it awards a point value after you clear the final virus from each level. This mechanic was removed prior to Dr. Mario’s release.
The virus characters are in an early state. They hang out in an oval (changed to a magnifying glass in Dr. Mario), and while they animate, they do not move in a circular motion, as they do in Dr. Mario.
Bring up the options screen for the two-player mode and you’re greeted with a familiar tune: it’s the menu music from Nintendo World Championships 1990! This track was also used in the Japan-only Famicom release Hello Kitty World. Nintendo was quite fond of that song, apparently.
Dr. Mario’s two-player win music isn’t yet implemented in Virus. Instead, the game uses the background music from Dr. Mario’s single-player intermission scenes. These scenes are not found in Virus.
Other differences:
- Mario’s sprite is different.
- The game keeps track of pills above the screen, so if you rotate them and one goes off the top, it’ll fall back down when there’s room.
- The highest levels allow pills up to the third line of the bottle, so you have to clear them horizontally (there’s no room).
- The background doesn’t switch colors to indicate difficulty level.
- The pill drop timer in hard mode is 10 frames in Virus, as opposed to 14 in Dr. Mario.
- Song A ("Fever"
is longer in Virus than it is in Dr. Mario.
- Two unused music tracks are present in the Virus ROM.