About

The Brain-chek puzzles consist of a 5x4 square grid, and a slider that can move along the edges of that grid. Each square has a dial, spot or other marker that changes whenever the slider moves along an edge of that square. There are several versions. The markers of the Stoplight version (pictured above left) are pictures of stoplights which obviously have 3 states, red, yellow, green. A move along an edge of a stoplight in the clockwise direction will make it change its colour from red to green, green to yellow, or yellow back to red. A move in the opposite direction changes the light the other way. The aim is of course to make all the lights green (or all red), preferably ending with the slider at a corner. The PhD version, pictured above middle, has both arrows and dots. The arrows have three states, and turn one step in the same direction as the direction you move the slider along an edge, similar to the Stoplight version. The dot in the centre only has two states (white or green in the picture), and changes with every move along the square's edge. Combined, the arrow and dot give each square six states. There are also versions with just the dots, either with pictures eyes that open or close, or of faces with noses that change colour. Lastly, there is a version where you can select the difficulty by choosing one of three sliders - one slider changes only dots, another only arrows, the third changes both. The sliders are stored in little compartements at the top of the puzzle, and can be inserted onto the grid by removing a small piece of the bottom edge of the frame. This puzzle is a remarkable piece of mechanical design. There is a clever mechanism that locks the arrows/dots in place, and which is only released when the slider passes by. This ensures that the arrows/dots are never dislodged unintentionally. Steven Kunreuther is the inventor/designer of the puzzle. It has taken him a long time to market it, so many of the variants of this puzzle that have found their way into puzzle collectors' hands are from relatively small prototype batches that were produced in order to promote it to puzzle manufacturers and distributors. The version with three sliders of varying difficulty has been produced in Taiwan under the name Magic Path by Getin Fun Creativity Co. There is some interesting mathematics behind this puzzle. There is an explanation of it after the solution below. [Skip to the maths section.] If your browser supports JavaScript, then you can play Brain-chek by clicking the link below: