The game is essentially a simulation of an ant colony. The game consists of three modes: a Quick Game, a Full Game, and an Experimental Game.
In SimAnt, the player plays the role of an ant in a colony of black ants in the back yard of a suburban home. The ant colony must battle against enemy red ants. The ultimate goal is to spread throughout the garden, into the house, and finally to drive out the antlions, spiders and human owners.
In the Quick Game, the player establishes a black ant colony in a small patch of yard, shown in top-down perspective. The computer opponent establishes a competing red ant colony in the same patch. Underground ant colonies are depicted in a side view. The player has direct control of a single ant at a time, indicated by a yellow color, and may switch control to a different ant at any time (by double-clicking the desired ant). (A little known fact is that the spider in the game can also be controlled by choosing Exchange from the Yellow Ant menu and clicking on it.) The player's yellow ant may influence the behavior of other black ants by leaving pheromone trails to destinations such as food and enemy ant colonies and can control the other ants in a limited way (by ordering a certain number to follow it, for instance). The quick game is won or lost when either the red or black colony in said patch is defeated.
The player's yellow ant may pick up food and pebbles, engage in trophallaxis (by receiving regurgitated food from friendly ants), and attack enemy ants. Groups of ants (or yellow ant with his recruits) may attack and kill bigger enemies like spiders, caterpillars, and antlions. Natural hazards include human footsteps, electrical outlets, bugspray, spiders, antlions, lawnmowers, and rain, which washes away pheromone trails and can flood the bottom of ant nests.
In the Full Game, the player begins with an ant colony in an overhead view, much like the Quick Game. The region of this overhead view is a single square of a map containing a yard and house. The player spreads to other areas by producing young queens and drones to mate with each other. The full game is lost when the black colonies are eliminated and won when the red colonies are eliminated and the humans are driven out of the house.
The Experimental Game is similar to the Quick Game, except the player can also control red ants and has access to a set of experimental tools. These tools allow the player to place pheromone trails, maze walls, rocks, ants, pesticides and food.