APOC 2023 – Round 10 : Calvin Koh vs Ivan Chan

Written by George Ortiz

The inaugural Asia-Pacific Othello Championships took place last month in Ulaanbaatar, Mongolia with a total of 114 players representing 8 different countries. 
Reigning world champion Kento Urano of Japan won the tournament undefeated, winning the final in two straight games against his compatriot Shun Souda.

Australia was represented by our AOF President Ivan Chan and he did us proud, finishing equal 17th overall (with 7 wins from 11 rounds) and winning the bronze medal in the Division 2 category (for WOF ratings between 1000 and 1499). 

In round 10, the penultimate round, Ivan faced the young 15 year old Calvin Koh of Singapore. The game promised to be an exciting match between two players of roughly equal strength, both among the favourites in Division 2, and it didn’t disappoint. Ivan was playing white in this game.

     Calvin Koh (SGP)  34-30 Ivan Chan (AUS)

Moves 1 to 5 are known as the Rabbit opening, second only to the Tiger opening in popularity. Back in the 1970s the Japanese named the most common 5-move openings after the 12 Chinese zodiac signs they are meant to very loosely resemble (you might find it easier to recognise the animals after a few cups of Sake :-))

6. F5 The Mimura opening.

The standard response to the Rabbit is 6.C6 that leads to the well known lines of the Rose opening (named after US Othello legend Brian Rose). However Ivan prefers to avoid the Rose and goes “old school” with the Mimura opening that went out of fashion more than 40 years ago! This opening is named after Takuya Mimura who has the dubious honour of being the first Japanese champion to lose a world championship final, losing the 1980 WOC final to Jonathan Cerf of the USA. 

Moves 7 to 10 are the classic continuation of the Mimura opening. So far the game is following the same 10 opening moves as the Cerf-Mimura 1980 WOC final. The main reason this old opening has gone out of fashion is that computer analysis shows that if played correctly it gives black a significantly better position. With this choice of opening Ivan is gambling that his opponent will be “out of book” early and will make a few mistakes giving white an early advantage. However so far it seems the young Singaporean had either seen this opening before or simply found the right moves.

Moves 11 to 29 : As we enter the midgame it becomes clear that Ivan’s opening gamble didn’t work out because Calvin made no significant mistakes and is in a better position with greater mobility. At move 29 Calvin takes advantage of the fact that the 4th row is completely white to move to the West edge with A4 threatening to “creep along the edge” and run white out of safe moves.

30. B5 is a bold but very nice move from Ivan to stay in the game. It takes away black’s move to F7 by flipping F5 and gets some central discs back on the 5th row. It doesn’t do anything however to prevent black from creeping along the West edge, on the contrary it even invites black to do so. Ivan probably realised that if black takes the West edge his position will slowly deteriorate as all further moves to the South will be “poisoned” (they will flip more discs than black would want).

Moves 31 to 36 : Calvin accepts Ivan’s invitation to gain tempos on the edge while Ivan plays out the few safe moves he has left to the South.

37. D7 is Calvin’s first significant mistake of the game. Calvin wanted to gain access to B6 by flipping the discs on the D column but failed to realise that his move to D7 also flips the 3 white discs on the E6-G4 diagonal giving white a nice move in H4.

38. H4 Ivan doesn’t miss it and starts to come back in the game.

39. G2 Calvin makes another mistake with his X-square move to G2 and for the first time in the game gives away the lead. The idea behind Calvin’s G2 is to avoid playing to the South to limit white’s mobility but it doesn’t work as white can respond with the very tricky 40.B6!!! B6 threatens to “swindle” (play multiple times in the same region) black in the North-East as it gains access to the H1 corner while also removing black’s access to H2. After B6 black would be forced to play to the South to regain access to H2 to avoid the swindle. Calvin should’ve played G2 two moves earlier rather than his D7 before white had access to H2.

40. H2 Ivan doesn’t find B6 but is still winning 33-31 with H2. The idea of H2 is to gain a tempo on the East edge while the 2nd row is all black and try to gain access to H1 later on.

Moves 41 to 43 : Ivan loses the lead with 42.C8 (the winner was still B6 to threaten to take H1) but Calvin fails to find the only winning move (43.D8) and gives the lead back to Ivan with 43.B6.

          White to play and win 33-31…

At move 44, Ivan has one last chance to win the game 33-31. Try to see where you would play in the above position, before reading on…..

To win the game you need to get to H1 so you could start by playing 44.C7 to cut the C6-G2 diagonal. If black defends the diagonal with 45.B7 white can cut it again with 46.B1 sacrificing A1 but gaining access to both H1 and A8 and getting “parity” (playing the last move) in almost every region of the board. So C7 is one of the winning moves, the other one being D8 which simply delays the move to C7 after first feeding the South edge to black.

44. F8 loses the game for Ivan. The problem with F8 is that it seals white off the South-East region of 5 empty squares (near H8). When white closes off an odd-numbered region of empty squares he runs the risk of losing parity, as black will be able to force white to pass in the last moves and get the last move of the game.

Moves 45 to 60 The endgame is played almost perfectly and Calvin wins the game 34-30.

Ivan did well in this game to come back from a very dire position and set himself up for the win but unfortunately failed to find it.

Both players reached the Division 2 semi-finals with Ivan eventually taking the bronze medal and Calvin winning the gold. Calvin also won a second gold medal as the best Junior player (under 16).

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