hello world project for programmers coding for a new system or programming language. This has resulted in the availability of a large number of ports for different platforms. For instance, μTorrent and GNU Emacs contain similar shape-stacking games as easter eggs. Within official franchise installments, each version has made improvements to accommodate advancing technology and the goal to provide a more complete game. Developers are given freedom to add new modes of play and revisit the concept from different angles. Some concepts developed on official versions have been integrated into the Tetris guidelines in order to standardize future versions and allow players to migrate between different versions with little effort. The IBM PC version was the most evolved from the original version, featuring a graphical interface, colored tetrominoes, running statistics for the number of tetrominoes placed, and a guide for the controls. In 2020 the intellectual property of the license belongs to Blue Planet Software. Maya (daughter of Rogers) supervises licenses to developers controlling their products. Computational complexity In computer science, it is common to analyze the computational complexity of problems, including real life problems and games. It was proven that for the "offline" version of Tetris (the player knows the complete sequence of pieces that will be dropped, i.e. there is no hidden information) the following objectives are NP-complete: Maximizing the number of rows cleared while playing the given piece sequence. Maximizing the number of pieces placed before a loss occurs. Maximizing the number of simultaneous clearing of four rows. Minimizing the height of the highest filled grid square over the course of the sequence. Also, it is difficult to even approximately solve the first, second, and fourth problem. It is NP-hard, given an initial gameboard and a sequence of p pieces, to approximate the first two problems to within a factor of for any constant . It is NP-hard to approximate the last problem within a factor of for any constant . To prove NP-completeness, it was shown that there is a polynomial reduction between the 3-partition problem, which is also NP-complete, and the Tetris problem. Music The earliest versions of Tetris had no music. The NES version includes two original compositions by Hirokazu Tanaka along with an arrangement of "Dance of the Sugar Plum Fairy" from the second act of The Nutcracker, composed by Tchaikovsky. The Tengen version also features original music, and an arrangement of "Kalinka"