From Wikipedia:
Ms. Pac-Man is an arcade video game produced by Midway as an unauthorized sequel to Pac-Man. It was released in North America in 1981 and became one of the most popular video games of all time, leading to its adoption by Pac-Man licensor Namco as an official title. This game introduces a female protagonist, new maze designs and several minor gameplay changes over the original game.
The first level of Ms. Pac-Man.The gameplay of Ms. Pac-Man is largely identical to that of the original Pac-Man. The player gathers points by eating dots and avoiding ghosts (contact with one loses a life). Power-pellets or energizers change the ghosts, which reverse their course and can be eaten for bonus points. Fruit bonuses can be consumed for increasing point values, twice per level. As the levels increase, the speed and difficulty increase as well.