ColorSwitch is an iOS/watchOS app written in Swift released in 2014. It is a fast-paced brain teaser based off of the Stroop Effect. Since its release, it has amassed over 500,000 downloads from countries around the world.
In psychology, the Stroop effect is a demonstration of cognitive interference where a delay in the reaction time of a task occurs due to a mismatch in stimuli.
ColorSwitch gamifies this effect by challenges the user by presenting a color as a word but having it colored in a different color. For example, the word "Blue" is printed in a green color. The user needs to select the blue tile instead of the green tile.