Microbes is an After Dark® module which eats your screen.
"Culture Size" limits the total number of microbes on the screen. This prevents the culture from growing exponentially until it consumes the entire screen, all of your free memory, and every clock cycle of the processor. It also keeps the animation at a pleasing pace.
"Visible" makes the microbes visible. Otherwise, you just see their omnivorous efforts. To prevent the screen from going completely blank, new (spontaneously created) microbes are visible until they eat something.
"Screen" controls what happens to the screen when the screen saver kicks in. "Leave" does nothing to the screen, and lets the microbes just eat what's there. "Invert" inverts the entire screen and lets the microbes eat what's not there. "Blank" erases the screen. "50%" erases every other pixel. And, "Fill" fills the entire screen with white pixels.
"Options…" brings up a dialog which lets you set additional characteristics:
"Size" selects the size of the microbes.
"Color" allows you to select the color of the microbes. If at least one monitor is set to display 4 or more colors/grays then you may select the color of all microbes with the "Set" button. If at least one monitor displays 256 or more colors/grays then you may select a "Healthy" color and a "Starving" color with the respective buttons. As the Microbes eat or starve, their color will drift between the two settings.
If you liked feeding the ants in an ant farm when you were younger (or older), and would like to do the same for your microbes, check the "Feed Starving Microbes" check box. When the microbe colony begins starving to death, After Dark will feed them clip art from the selections below. Cut or paste pictures into the list from other applications or the clipboard. Paste in a picture of your boss.
"Erase Before Drawing" erases the screen to white before drawing the picture. Since many pictures are just black lines, drawing black on black doesn't accomplish much (unless your a minimalist artist).
"Invert" inverts the picture after it's drawn. This makes pictures made of black lines into pictures made of white lines. The microbes eat the lines, not the background, which is probably what you want (unless your an artist exploring negative space).
A word about microbe life...
Microbes search for food in adjacent (touching) positions on the screen. If they find food, they go there. Given a choice between two locations, a microbe will prefer the richest (most luminous) position. When they can't find any food, Microbes wander aimlessly in the hopes that they will bump into some. Eating strong food makes them healthier, while very weak food or no food at all taxes their energy reserves. When a microbe's reserves fall too low they begin to slow down and will eventually die.
They divide when they're fat (very healthy) and have reached a minimum age (no child biology here). The two sister microbes generated from a division each have half the energy reserves as the parent and start over at age 0. Like all organisms, microbes have a life expectancy; If they fail to divide for an extended period of time, they will simply die of old age.
When all of the microbes are starving, the module "seeds" the screen with new, spontaneously created, microbes. In fact, this is how the whole process is started to begin with. As long as some microbes are eating, no new microbes are created. This lets each active colony run it's course.
When the screen is nearly empty (this assumes your not feeding your microbes clip art) random chance will make it almost impossible to clear the screen. The probability of a single pixel microbe stumbling across any single screen pixel are, well, real bad. To make this "end game" more efficient, the module quietly and methodically searches the screen for stray food bits and tends to create new microbes right next to them.
