Stroop is a real-time observation game based on the psychological Stroop Effect, which is a phenomenon caused by different functions of the brain interfering with one another.

The cards in Stroop each display a single word. The words are printed in several colors (black, red, blue, and yellow), sizes (big and little), styles (hollow and solid) and have different numbers of letters (three, four, five, and six). The challenge is to read one word and quickly match it with the description of another wordwithout regard to what the second word says.