And instead of a drag on the bottom line, Roomba has subsidized the development of what Angle hopes is the next big step for iRobot: health care.

FORBES: Invasion Of The Machines: iRobot Hunts Bombs, Cleans Floors, Now Wants To Heal You

You update your internal picture, perhaps changing the angle of some of a line here or there, or adding another element.

FORBES: Your Brain Was Made For Visual Modeling

For instance, the kiosk explains that Rothermel's deliberate perspective puts the viewer 125 yards from the copse of trees just below Cemetery Ridge in an area of the battle line known as "the Angle, " a jog in the stone wall defended by the Philadelphia Brigade.

WSJ: Capturing Gettysburg | Objects of Valor | State Museum of Pennsylvania | By Mark Yost