Number Munchers is an educational game initially made available for DOS, Apple II and Mac computers, designed for children 8 years of age and older. Winner of the Classroom Computer Learning Readers' Choice Award for Programs of the Decade, Number Munchers was the archetypal math game of the 1980's -- Oregon Trail and the Carmen Sandiego series hold this honour for their respective genres. Later, Fraction Munchers, Word Munchers and Math Munchers would appear.

Created by MECC (the Minnesota Educational Computing Corporation, now The Learning Company) in the mid eighties, Number Munchers promotes rudimentary math and motor skills. From the box:

With the Muncher's help, you'll learn basic math skills the fun and exciting way. Earn points as your Muncher matches and munches multiples, factors, primes, equalities, and inequalities. But there's trouble brewing all around the game board. Mischevious Troggles will stop at nothing to make it difficult for you and your Muncher to maneuver successfully through the games. And if you earn enough points, you could even qualify for the Muncher Hall of Fame.
The player navigates their Number Muncher through a six-by-five grid using the arrow keys or a joystick, eating (removing) all of the functions that conform to that level using the space bar. In the first three levels, only one Troggle appears. In levels four through seven, two Troggles appear and in levels eight and higher, the player must contend with three Troggles. May God have mercy on your soul.

Each level can be of five types:

Every three levels, an amusing cutscene appears in which Troggles are defeated in a humourous manner.

A typical Number Munchers level appears:

Level: 3      Equals 7
+------+------+------+------+------+------+
|      |      | 14/2 | 1x15 |      | 33-9 |
+------+------==----==------+------+------+
|      | 3+4  |      | 12+5 |      | 35/5 |
+------+------==----==------==----==------+
|      |      |  T   |      | 11/1 |      |
+------+------+------+------==----==------+
|  T   | 12-5 |      |      |  N   |      |
+------+------+------+------+------+------+
| 1+6  | 7-0  |      | 5+2  | 14-7 | 49/7 |
+------+------+------+------+------+------+
Score: 350
Where
T = a Troggle
N = the player's Number Muncher

Regions surrounded by '='s are safety zones -- Troggles that attempt to enter one of these squares disappear.

The Cast:
Number Muncher (Munchicus digitus)

The Troggles:

Reggies (Trogglus normalus)

Reggie Troggles cross the playing field, leaving different problems in their wake.
Bashfuls (Trogglus timidus)
Like Reggie Troggles, Bashful Troggles also wander across the playing field changing problems.
Smarties (Trogglus smarticus)
Smartie Troggles follow the Number Muncher in an attempt to catch it.
Helpers (Trogglus assistus)
Helper Troggles cross the playing field, removing problems.
Workers (Trogglus laborus)
Helper Troggles cross the playing field, adding new problems.
One unattributed 'cheat' for Number Munchers is circulating:
The player can pass through Troggles headed straight towards them when the Troggle is approaching from an adjacent square.
Of course, here's the obligatory poor ASCII Art representation of the protagonist (generated via a tool named ASCII Pic 2.0 and massaged by hand):

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########################## 
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See my home node pic for a shot of the Number Munchers hero.