The object is to exchange the blue triangle with the red triangle. The tiles travel along the black channels and may not jump over other tiles. The tiles will automatically move down to the lowest position possible in a column. What makes the puzzle difficult is that a tile will not move below it's initial starting position.
This puzzle was made in Japan by a magic company a few years ago. An important difference is that they used ten tiles for each triangle. This makes solving it a long and arduous process. (about 30,000 moves! yikes!) Using only four tiles makes this a nice puzzle that is frustrating but quite possible to solve in an afternoon or so.