**Reference**:- Erik D. Demaine, Susan Hohenberger, and David Liben-Nowell, “Tetris is Hard, Even to Approximate”, in
*Proceedings of the 9th International Computing and Combinatorics Conference (COCOON 2003)*, Big Sky, Montana, July 25–28, 2003, pages 351–363. **Abstract**:-
In the popular computer game of
*Tetris*, the player is given a sequence of tetromino pieces and must pack them into a rectangular gameboard initially occupied by a given configuration of filled squares; any completely filled row of the gameboard is cleared and all pieces above it drop by one row. We prove that in the offline version of Tetris, it is NP-complete to maximize the number of cleared rows, maximize the number of tetrises (quadruples of rows simultaneously filled and cleared), minimize the maximum height of an occupied square, or maximize the number of pieces placed before the game ends. We furthermore show the extreme inapproximability of the first and last of these objectives to within a factor of*p*^{1 − ε}, when given a sequence of*p*pieces, and the inapproximability of the third objective to within a factor of 2 − ε, for any ε > 0. Our results hold under several variations on the rules of Tetris, including different models of rotation, limitations on player agility, and restricted piecesets. **Updates**:- Ivars Peterson wrote an article describing these results, “Tetris Is Hard”,
*Science News*162(17), October 26, 2002.Helen Pearson also wrote an article describing these results, “Maths proves Tetris is tough”,

*Nature Science Update*, October 28, 2002.Sarah Graham also wrote a short article describing these results, “Mathematicians Prove Tetris is Tough”,

*Scientific American News*, October 29, 2002. **Length**:- The paper is 12 pages.
**Availability**:- The paper is available in PostScript (1330k), gzipped PostScript (97k), and PDF (217k).
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**Related papers**:- Tetris_IJCGA (Tetris is Hard, Even to Approximate)
- Tetris_CGW2002 (Tetris is Hard, Even to Approximate)
- Tetris_TR2002 (Tetris is Hard, Even to Approximate)

See also other papers by Erik Demaine.

Last updated November 1, 2014 by Erik Demaine.