Tetris turned 30 years old on June 6, which is known as World Tetris Day.

Despite its age, Tetris retains popularity because of its usage of the "Zeigarnik effect."

According to the "Zeigarnik effect," people have better memories of tasks that they were not able to complete, as opposed to tasks that they were able to finish.

"Tetris does this wonderfully ... it presents a world of perpetual uncompleted tasks," said Dr. Tom Stafford from the University of Sheffield's Department of Psychology.

"It shows how our minds are organized around goals and that our memory is not just a filing system where information is passively stored, but it adjusts dynamically according to our purposes."

Stafford applauds the genius behind Tetris, which takes advantage of the "Zeigarnik effect" to create a game that keeps players hooked as tasks that are completed are instantly replaced with more tasks.

"Tetris is pure game: there is no benefit to it, nothing to learn, no social or physical consequence. It is almost completely pointless, but keeps us coming back for more."

The last 30 years have seen players from different generations take their crack at the game, which despite having the simple goal of filling in gaps in bricks with falling pieces, has grown to be one of the best-selling games of all time.

Previous research done on Tetris has found out that people play the game in two ways. The first way is to rotate the falling piece in your mind into the correct position before rotating the piece in the game. The second way, which is the more popular way, is to keep pushing the button to compare the shape of the falling piece with the gaps in the bricks.

Alexey Pajitnov, the creator of Tetris, revealed in an interview with The Guardian that Tetris was born out of a computing lab for the Academy of Science of the former USSR. Pajitnov was writing programs to test new hardware, and one of his projects was Tetris. He based it on the popular Pentominoes game, and before long, he and his colleagues were hooked on it.

"Tetris came along early and had a very important role in breaking down ordinary people's inhibitions in front of computers, which were scary objects to nonprofessionals used to pen and paper. But the fact that something so simple and beautiful could appear on screen destroyed that barrier," Pajitnov said.