Citizendia
Your Ad Here

Reversi/Othello

Screenshot of Iagno running on ubuntu
Players 2
Age range Recommended for 8 years or older
Setup time None
Playing time 10-60 minutes
Random chance None
Skills required Strategy, Observation

Reversi (also known as Othello) is an abstract strategy board game which involves play by two parties on an eight-by-eight square grid with pieces that have two distinct sides. Ubuntu Kubuntu Edubuntu Xubuntu Gobuntu --> Ubuntu An abstract strategy game is a board or card game with Perfect information, no chance and (usually two players or teams An abstract strategy game is a board or card game with Perfect information, no chance and (usually two players or teams A board game is a Game in which counters or pieces that are placed on removed from or moved across a "board" (a premarked surface usually specific to that game Pieces typically appear coin-like, but with a light and a dark face, each side representing one player. The object of the game is to make your pieces constitute a majority of the pieces on the board at the end of the game, by turning over as many of your opponent's pieces as possible.

Contents

Origins

The modern version of the game is based on the game Reversi that was invented around 1880 by two Englishmen, Lewis Waterman and John W. Mollett, and gained considerable popularity in England at the end of the 19th century. The game is mentioned in an 1895 article in the New York Times: "Reversi is something like Go Bang, and is played with 64 pieces. "[1] In 1898, the well-known German games publisher Ravensburger started producing the game as one of its first titles. Ravensburger Spieleverlag GmbH is a German game company It is a leader in the European Puzzle market

The modern rule set, now universally accepted, originated in Mito, Ibaraki, Japan in the 1970s; the game was renamed Othello, and was registered as a trademark by the Japanese game company Tsukuda Original. is the capital of Ibaraki Prefecture, Japan and has a central location moderately offset towards the coast in that prefecture For a topic outline on this subject see List of basic Japan topics. This article is about the Decade 1970-1979 For the Year 1970 see 1970. A trademark or trade mark, represented by the symbols ™ and ®, or mark is a distinctive sign or indicator used by an individual The name is a reference to the Shakespearean play Othello, the Moor of Venice, referencing the conflict between the Moor Othello and Iago, who describes himself as "two faced" (or more controversially, to the marriage between Othello, who is black, and Desdemona, who is white, recalling the coloring of the game pieces). William Shakespeare ( baptised The description Moors has referred to several historic and modern populations of Muslim (and earlier non-Muslim people of Berber and Arab descent It can also be likened to a jealousy competition (jealousy being the central theme in Shakespeare's play) since players engulf the pieces of the opponent, thereby turning them their possession.

A 2002 press release about the origins of the modern game makes no mention of the original version: [2]

Othello(R) was invented by Japanese game enthusiast, Goro Hasegawa in 1971. He chose one of the leading toy inventors in the world, James R. Becker, to help him develop and market the game. Inspired by the ancient Japanese strategy game 'Go', Hasegawa sought to create a game that was rich in strategy, but still approachable by the casual player. Becker simplified the game play, coined the tagline, 'A Minute to Learn. . . A Lifetime to Master'(R) and named this new game after Shakespeare's classic play, because of the black and white chips. Othello(R) was first introduced in Japan in 1973, by Tsukuda Original Co. , who at Becker's suggestion organized the Japanese Othello(R) Association.

Goro Hasegawa, who wrote How to win at Othello, popularized the game in Japan in 1975. For a topic outline on this subject see List of basic Japan topics. Year 1975 ( MCMLXXV) was a Common year starting on Wednesday (link will display full calendar of the Gregorian calendar.

Play

Each of the two sides corresponds to one player; they are referred to here as light and dark after the sides of Othello pieces, but "heads" and "tails" would identify them equally as well, so long as each marker has sufficiently distinctive sides.

Originally, Reversi did not have a defined starting position. Later it adopted Othello's rules, which state that the game begins with four markers placed in a square in the middle of the grid, two facing light-up, two pieces with the dark side up. The dark player makes the first move.

Image:chess_zhor_22.png
Image:Othello_zver_22.png
a8 b8 c8 d8 e8 f8 g8 h8
a7 b7 c7 d7 e7 f7 g7 h7
a6 b6 c6 d6 e6 f6 g6 h6
a5 b5 c5 d5 e5 f5 g5 h5
a4 b4 c4 d4 e4 f4 g4 h4
a3 b3 c3 d3 e3 f3 g3 h3
a2 b2 c2 d2 e2 f2 g2 h2
a1 b1 c1 d1 e1 f1 g1 h1
Image:Othello_zver_22.png
Image:chess_zhor_22.png
Starting position

Dark must place a piece with the dark side up on the board, in such a position that there exists at least one straight (horizontal, vertical, or diagonal) line between the new piece and another dark piece, with one or more contiguous light pieces between them. In the below situation, dark has the following options indicated by transparent pieces:

Image:chess_zhor_22.png
Image:Othello_zver_22.png
a8 b8 c8 d8 e8 f8 g8 h8
a7 b7 c7 d7 e7 f7 g7 h7
a6 b6 c6 d6 e6 f6 g6 h6
a5 b5 c5 d5 e5 f5 g5 h5
a4 b4 c4 d4 e4 f4 g4 h4
a3 b3 c3 d3 e3 f3 g3 h3
a2 b2 c2 d2 e2 f2 g2 h2
a1 b1 c1 d1 e1 f1 g1 h1
Image:Othello_zver_22.png
Image:chess_zhor_22.png
Where dark may play

After placing the piece, dark turns over (flips, captures) all light pieces lying on a straight line between the new piece and any anchoring dark pieces. All reversed pieces now show the dark side, and dark can use them in later moves -- unless light has reversed them back in the meantime.

If dark decided to put a piece in the topmost location (all choices are strategically equivalent at this time), one piece gets turned over, so that the board appears thus:

Image:chess_zhor_22.png
Image:Othello_zver_22.png
a8 b8 c8 d8 e8 f8 g8 h8
a7 b7 c7 d7 e7 f7 g7 h7
a6 b6 c6 d6 e6 f6 g6 h6
a5 b5 c5 d5 e5 f5 g5 h5
a4 b4 c4 d4 e4 f4 g4 h4
a3 b3 c3 d3 e3 f3 g3 h3
a2 b2 c2 d2 e2 f2 g2 h2
a1 b1 c1 d1 e1 f1 g1 h1
Image:Othello_zver_22.png
Image:chess_zhor_22.png
After dark play

Now light plays. This player operates under the same rules, with the roles reversed: light lays down a light piece, causing one or more dark pieces to flip. Possibilities at this time appear thus (indicated by "ghosts"):

Image:chess_zhor_22.png
Image:Othello_zver_22.png
a8 b8 c8 d8 e8 f8 g8 h8
a7 b7 c7 d7 e7 f7 g7 h7
a6 b6 c6 d6 e6 f6 g6 h6
a5 b5 c5 d5 e5 f5 g5 h5
a4 b4 c4 d4 e4 f4 g4 h4
a3 b3 c3 d3 e3 f3 g3 h3
a2 b2 c2 d2 e2 f2 g2 h2
a1 b1 c1 d1 e1 f1 g1 h1
Image:Othello_zver_22.png
Image:chess_zhor_22.png
Where light may play

Light takes the bottom left option and reverses one piece:

Image:chess_zhor_22.png
Image:Othello_zver_22.png
a8 b8 c8 d8 e8 f8 g8 h8
a7 b7 c7 d7 e7 f7 g7 h7
a6 b6 c6 d6 e6 f6 g6 h6
a5 b5 c5 d5 e5 f5 g5 h5
a4 b4 c4 d4 e4 f4 g4 h4
a3 b3 c3 d3 e3 f3 g3 h3
a2 b2 c2 d2 e2 f2 g2 h2
a1 b1 c1 d1 e1 f1 g1 h1
Image:Othello_zver_22.png
Image:chess_zhor_22.png
After light play

Players take alternate turns. If one player cannot make a valid move, play passes back to the other player. When neither player can move, the game ends. This occurs when the grid has filled up, or when one player has no more pieces on the board, or when neither player can legally place a piece in any of the remaining squares. The player with more pieces on the board at the end wins.

Strategy

A beginner often looks for the move that will reverse the greatest possible number of pieces, trying for immediate numerical advantage. For unsophisticated players, this strategy works quite well and will win a majority of games as long as the player thinks at least a few turns in advance. Against extremely experienced players, however; this strategy has been shown to only win about 45% of games.

While it is possible to achieve complete dominance early and capture all the tiles, it is extremely unlikely. Instead of numerical advantage, the key elements of successful Othello strategy are corners, mobility, edge play, parity, endgame play, and looking ahead.

Corners

Corner positions, once played, remain immune to flipping for the rest of the game (because there is no other opposite color behind them to create a flip): thus a player can use a piece in a corner of the board to anchor groups of pieces (starting with the adjacent edges) permanently. So capturing a corner often proves an effective strategy when the opportunity arises. More generally, a piece is stable when, along all four axes (horizontal, vertical, and each diagonal), it is on a boundary, in a filled row, or next to a stable piece of the same color. Grabbing a corner too soon can be a mistake, however, if it leaves "holes" in the edge that the opponent can make use of.

Mobility

An opponent playing with reasonable strategy will not so easily relinquish the corner or any other good moves. So to achieve these good moves, you must force your opponent to play moves which relinquish those good moves. The best way to achieve this involves reducing the number of moves available to your opponent. If you consistently restrict the number of legal moves your opponent can make, then sooner or later they will have to make an undesirable move. An ideal position involves having all your pieces in the center surrounded by your opponent's pieces. In such situations you can dictate what moves your opponent can make.

When moves seem equal with respect to what moves you will leave yourself and your opponent, playing a minimum piece strategy will tend to give you an advantage, because minimizing your discs will tend to leave fewer discs for your opponent to flip in subsequent moves of the game. One should not play the minimum disc strategy to an extreme, however, as this also can quickly lead to a lack of mobility.

Edges

While playing pieces to edges of the board may seem sound (because they cannot be flipped easily), this strategy can often prove detrimental. Edge pieces can anchor flips that influence moves to all regions of the board. This can poison later moves by causing players to flip too many pieces and open up many moves for the opponent. However, playing on edges where an opponent cannot easily respond drastically reduces possible moves for that opponent.

The square immediately diagonally adjacent to the corner (called the X-square), when played in the early or middle game, typically guarantees the loss of that corner. Nevertheless, such a corner sacrifice is sometimes played for some strategic purpose (like retaining mobility). Playing to the edge squares adjacent to the corner (called the C-squares) can also be dangerous if it gives the opponent powerful forcing moves.

In general, edge play in the early and middle game is to be avoided, unless players can gain larger concessions in terms of mobility or a mass of unflippable pieces.

A good rule of thumb is to keep pieces grouped together in the middle of the board and minimize tangents formed by a player's own pieces. This strategy leads to the greatest mobility.

Parity

Parity is one of the most important parts of the strategy. In short, the concept of parity is about getting the last move in every empty region in the end-game, and thereby increasing the number of stable discs.

In the late 1980s the concept of parity was spread across Europe (from Japan). It was a new paradigm that changed the game forever.

The concept of parity led to a change in the perception of the game, as it led to distinct strategies for playing black and white. It forced black to play more aggressive moves and gave white the opportunity to stay calm and focus on keeping the parity. As a result the opening books and mid-game were focused on black being the "attacker" and white being the "defender".

Another side effect of parity is that black should try to complicate the game whereas white should seek to simplify it. It is easier to maintain parity in a simple position.

The concept of parity also controls how edge positions are played and how edges interact.

Today it is essential to have an understanding of parity to get the maximum experience out of the game.

Emmanuel Lazard has written a booklet with an in-depth description of parity.

Look-ahead

As in any good strategy for chess or for checkers, a player should not consider only the current situation on the board. Chess is a recreational and competitive Game played between two players. For each move you consider, you must consider possible responses from your opponent, then the subsequent responses you will make to those moves and so on. The aspects of the current position may not remain relevant a few moves hence. So when optimizing your mobility, gaining corners or anything else, you should consider how best to do this for the long term rather than just for the next move.

Endgame

For the endgame (the last 20 or so moves of the game) the strategies will typically change. Special techniques such as sweeping, gaining access, and the details of move-order can have a large impact on the outcome of the game. At these late stages of the game no hard-set rules exist. The experienced player will try to look ahead and get a feel for what will lead to the best final outcome.

Computer opponents

The best Othello computer programs can easily defeat the best humans. As early as 1980, the program The Moor beat the reigning world champion. In 1997, Logistello defeated the human champion Takeshi Murakami in a score of 6:0. Logistello is a computer program that plays the game Othello, also known as Reversi By comparison, computers also easily win against the best human players of English draughts (checkers), but in chess the computers are only somewhat better than the best humans, and in Go and Arimaa even average human players can defeat the best computers. Chess is a recreational and competitive Game played between two players. Arimaa is a two-player Abstract strategy Board game that can be played using the same equipment as Chess.

Human beings cannot generally win against computer intelligence in Othello because computers can look ahead much further than humans can. Analysts have estimated the number of legal positions in Othello is at most 1028, and it has a game-tree complexity of approximately 1058. Combinatorial game theory has several ways of measuring game complexity. [3]

Mathematically, Othello still remains unsolved. A two player Game can be " solved " on several levels; Ultra-weak In the weakest sense solving a game means proving whether the first player will win Experts have not yet figured out what the outcome of a game will be where both sides have perfect play. A two player Game can be " solved " on several levels; Ultra-weak In the weakest sense solving a game means proving whether the first player will win However, analysis of thousands of high-quality games (most of them computer-generated) has led to the conclusion that, on the standard 8-by-8 board, perfect play on both sides results in a draw[4]. When generalizing the game to play on an n-by-n board, the problem of determining if the first player has a winning move in a given position is PSPACE-complete. In Computational complexity theory, a generalized game is a game that has been generalized so that it can be played on a board of any size Mathematicians and computer scientists try to carefully define different types of complexity and PSPACE-complete is one of these types [5] On 4-by-4 and 6-by-6 boards under perfect play, the second player wins.

Console game releases

Trivia

World Othello Championship

Year Location World Champion Country Team Runner-Up Country
1977 Tokyo Hiroshi Inoue Japan N/A Thomas Heiberg Norway
1977* Monte Carlo Sylvain Perez France N/A Michel Rengot (Blanchard) France
1978 New York Hidenori Maruoka Japan N/A Carol Jacobs USA
1979 Rome Hiroshi Inoue Japan N/A Jonathan Cerf USA
1980 London Jonathan Cerf USA N/A Takuya Mimura Japan
1981 Brussels Hidenori Maruoka Japan N/A Brian Rose USA
1982 Stockholm Kunihiko Tanida Japan N/A David Shaman USA
1983 Paris Ken'Ichi Ishii Japan N/A Imre Leader Britain
1984 Melbourne Paul Ralle France N/A Ryoichi Taniguchi Japan
1985 Athens Masaki Takizawa Japan N/A Paolo Ghirardato Italy
1986 Tokyo Hideshi Tamenori Japan N/A Paul Ralle France
1987 Milan Ken'Ichi Ishii Japan USA Paul Ralle France
1988 Paris Hideshi Tamenori Japan Britain Graham Brightwell Britain
1989 Warsaw Hideshi Tamenori Japan Britain Graham Brightwell Britain
1990 Stockholm Hideshi Tamenori Japan France Didier Piau France
1991 New York Shigeru Kaneda Japan USA Paul Ralle France
1992 Barcelona Marc Tastet France Britain David Shaman Britain
1993 London David Shaman USA USA Emmanuel Caspard France
1994 Paris Masaki Takizawa Japan France Karsten Feldborg Denmark
1995 Melbourne Hideshi Tamenori Japan USA David Shaman USA
1996 Tokyo Takeshi Murakami Japan Britain Stephane Nicolet France
1997 Athens Makoto Suekuni Japan Britain Graham Brightwell Britain
1998 Barcelona Takeshi Murakami Japan France Emmanuel Caspard France
1999 Milan David Shaman Netherlands Japan Tetsuya Nakajima Japan
2000 Copenhagen Takeshi Murakami Japan USA Brian Rose USA
2001 New York Brian Rose USA USA Raphael Schreiber USA
2002 Amsterdam David Shaman Netherlands USA Ben Seeley USA
2003 Stockholm Ben Seeley USA Japan Makoto Suekuni Japan
2004 London Ben Seeley USA USA Makoto Suekuni Japan
2005 Reykjavík Hideshi Tamenori Japan Japan Kwangwook Lee South Korea
2006 Mito Hideshi Tamenori Japan Japan Makoto Suekuni Singapore
2007 Athens Kenta Tominaga Japan Japan Stephane Nicolet France

*This rivalling Monte Carlo world championship is usually not considered to be an official world championship. Also 1977 (album by Ash. Year 1977 ( MCMLXXVII) was a Common year starting on Saturday (link displays officially, is one of the 47 prefectures of Japan and located on the eastern side of the main island Honshū. Also 1977 (album by Ash. Year 1977 ( MCMLXXVII) was a Common year starting on Saturday (link displays Monte-Carlo ( Occitan: Montcarles, Monégasque: Monte-Carlu) is one of Monaco 's various administrative areas sometimes erroneously Year 1978 ( MCMLXXVIII) was a Common year starting on Sunday (link displays the 1978 Gregorian calendar) New York ( is a state in the Mid-Atlantic and Northeastern regions of the United States and is the nation's third most populous Carol Jacobs (born New York City) is a former American othello player Year 1979 ( MCMLXXIX) was a Common year starting on Monday (link displays the 1979 Gregorian calendar) Rome ( Roma ˈroma Roma is the capital city of Italy and Lazio, and is Italy's largest and most populous city with more than 2 Year 1980 ( MCMLXXX) was a Leap year starting on Tuesday (link displays the 1980 Gregorian calendar) London ( ˈlʌndən is the capital and largest urban area in the United Kingdom. Year 1981 ( MCMLXXXI) was a Common year starting on Thursday (link displays the 1981 Brussels (Bruxelles pronounced; Brussel pronounced) officially the Brussels Capital-Region, is Year 1982 ( MCMLXXXII) was a Common year starting on Friday (link displays the 1982 Gregorian calendar) ('stɔkhɔlm is Sweden 's Capital and its largest City. It is the site of the national Swedish government, the parliament, and the Year 1983 ( MCMLXXXIII) was a Common year starting on Saturday (link displays the 1983 Gregorian calendar) Paris (ˈpærɨs in English; in French) is the Capital of France and the country's largest city Imre Bennett Leader is a British Mathematician and Professor of Pure Mathematics at the University of Cambridge. Year 1984 ( MCMLXXXIV) was a Leap year starting on Sunday (link displays the 1984 Gregorian calendar) Melbourne ( is the second most populous city in Australia, with a Metropolitan area population of approximately 3 Year 1985 ( MCMLXXXV) was a Common year starting on Tuesday (link displays 1985 Gregorian calendar) Athens (ˈæθənz Αθήνα Athina,) the Capital and largest city of Greece, dominates the Attica periphery as one of the world's Year 1986 ( MCMLXXXVI) was a Common year starting on Wednesday (link displays 1986 Gregorian calendar) officially, is one of the 47 prefectures of Japan and located on the eastern side of the main island Honshū. Year 1987 ( MCMLXXXVII) was a Common year starting on Thursday (link displays 1987 Gregorian calendar) Milan (Milano Milan (listen) is one of the largest cities in Italy, located in the plains of Lombardy. Year 1988 ( MCMLXXXVIII) was a Leap year starting on Friday (link displays 1988 Gregorian calendar) Paris (ˈpærɨs in English; in French) is the Capital of France and the country's largest city Year 1989 ( MCMLXXXIX) was a Common year starting on Sunday (link displays 1989 Gregorian calendar) Warsaw (Warszawa; also known by other names) is the Capital and Largest city of Poland. Year 1990 ( MCMXC) was a Common year starting on Monday (link displays the 1990 Gregorian calendar) ('stɔkhɔlm is Sweden 's Capital and its largest City. It is the site of the national Swedish government, the parliament, and the Year 1991 ( MCMXCI) was a Common year starting on Tuesday (link will display full calendar of the Gregorian Calendar. New York ( is a state in the Mid-Atlantic and Northeastern regions of the United States and is the nation's third most populous Year 1992 ( MCMXCII) was a Leap year starting on Wednesday (link will display full 1992 Gregorian calendar) Barcelona ( Catalan bəɾsəˈlonə Spanish baɾθeˈlona is the capital and most populous city of the Autonomous Community of Catalonia Year 1993 ( MCMXCIII) was a Common year starting on Friday (link will display full 1993 Gregorian calendar) London ( ˈlʌndən is the capital and largest urban area in the United Kingdom. Year 1994 ( MCMXCIV) was a Common year starting on Saturday (link will display full 1994 Gregorian calendar) Paris (ˈpærɨs in English; in French) is the Capital of France and the country's largest city Year 1995 ( MCMXCV) was a Common year starting on Sunday. Events of 1995 Melbourne ( is the second most populous city in Australia, with a Metropolitan area population of approximately 3 Year 1996 ( MCMXCVI) was a Leap year starting on Monday (link will display full 1996 Gregorian calendar) officially, is one of the 47 prefectures of Japan and located on the eastern side of the main island Honshū. Year 1997 ( MCMXCVII) was a Common year starting on Wednesday (link will display full 1997 Gregorian calendar Athens (ˈæθənz Αθήνα Athina,) the Capital and largest city of Greece, dominates the Attica periphery as one of the world's Year 1998 ( MCMXCVIII) was a Common year starting on Thursday (link will display full 1998 Gregorian calendar) Barcelona ( Catalan bəɾsəˈlonə Spanish baɾθeˈlona is the capital and most populous city of the Autonomous Community of Catalonia Year 1999 ( MCMXCIX) was a Common year starting on Friday (link will display full 1999 Gregorian calendar) Milan (Milano Milan (listen) is one of the largest cities in Italy, located in the plains of Lombardy. 2000 ( MM) was a Leap year that started on Saturday of the Common Era, in accordance with the Gregorian calendar. Copenhagen (ˌkəʊpənˈheɪgən ˌkəʊpənˈhɑːgən ˈkəʊpənˌheɪgən ˈkəʊpənˌhɑːgən kʰøb̥ənˈhɑʊ̯ˀn kʰøb̥m̩ˈhɑʊ̯ˀn is the capital and largest city Year 2001 ( MMI) was a Common year starting on Monday according to the Gregorian calendar. New York ( is a state in the Mid-Atlantic and Northeastern regions of the United States and is the nation's third most populous See also 2002 (disambiguation Year 2002 ( MMII) was a Common year starting on Tuesday of the Gregorian calendar. Amsterdam (pronounced) is the capital and largest city of the Netherlands, located in the province of North Holland in the west Year 2003 ( MMIII) was a Common year starting on Wednesday of the Gregorian calendar. ('stɔkhɔlm is Sweden 's Capital and its largest City. It is the site of the national Swedish government, the parliament, and the "MMIV" redirects here For the Modest Mouse album see " Baron von Bullshit Rides Again " London ( ˈlʌndən is the capital and largest urban area in the United Kingdom. Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar. For the Greater Reykjavík Area see the Greater Reykjavík Area. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. is the capital of Ibaraki Prefecture, Japan and has a central location moderately offset towards the coast in that prefecture Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Athens (ˈæθənz Αθήνα Athina,) the Capital and largest city of Greece, dominates the Attica periphery as one of the world's In official homepages it is called the first Europe Championship.

Notes

  1. ^ "FINE NEW GAMES AND TOYS; Now Ready for Distribution by the Agents of Santa Claus. IN THE MODERN WONDERLAND Millions Spent for the Amusement and Instruction of Children -- Minds Active and Hands Busy All the Time", New York Times, December 1, 1895
  2. ^ "Othello: The World's Best Selling Licensed Strategy Game Lands in MDI Entertainment's Portfolio of Lottery Game Properties", December 4, 2002
  3. ^ Victor Allis (1994). Searching for Solutions in Games and Artificial Intelligence. Ph. D. Thesis, University of Limburg, Maastricht, The Netherlands. ISBN 9090074880.  
  4. ^ Edax-download
  5. ^ S. Iwata and T. Kasai (1994). "The Othello game on an n*n board is PSPACE-complete". Theor. Comp. Sci. 123 (123): 329–340. doi:10.1016/0304-3975(94)90131-7. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.  

References

External links

Dictionary

reversi

-noun

  1. A strategy game for two players, areas of the board being captured by surrounding rows of the opponent's pieces with one's own.
© 2009 citizendia.org; parts available under the terms of GNU Free Documentation License, from http://en.wikipedia.org
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic