Bestiary

Introduction
I. Extraordinary life and death problems.

1. Symmetrical problems 2. Snapbacks (uttegaeshi) 3. Under the stones (ishinoshita) 4. Eye reduction (nakade) 5. Blind spots 6. Reference positions 7. Most difficult classical problems

II. Paradoxical tesujis and strange manoeuvres.

1. First line moves 2. Shortage of liberties (damezumari) 3. Off-limits moves and phantom go 4. Impossible cuts (atekomi, warikomi, etc.) 5. Traps and variations of joseki 6. Extraordinary moves played in real games

III. Ladders and other incredible sequences.
IV. Semeais, sekis and pseudo-sekis.
V. Problems about rules.

Introduction

Here, you will only find my bestiary of interesting positions and problems (162 of them) ; go there for motivations, solutions and detailed commentaries.

While most of those problems are "artistic" ones, many of them are quite hard, so I thought useful to give a (very rough) indication of their difficulty : some easy reference positions are not ranked, but for the others :
one means the problem can be solved (in a reasonable time, without moving stones) by a player around 1k (52 problems),
two means a 5d level (57 problems),
three means a professional level (40 problems).
And, of course, Dosetsu's problem, and 12 others, are ranked ...

Appetizer : Black to play ; status ?
Solution and commentaries

I. Extraordinary life and death problems.

1. Symmetrical problems

Problem 1 : Black escapes         Solution and commentaries

Problem 2 : the mask, most difficult symmetrical problem (Black to play and save his five surrounded stones)   Solution and commentaries

Problem 3 : Black to play and kill Solution and commentaries	Problem 4 : Black to play and kill Solution and commentaries
Problem 5 : Black to play and escape   Solution and commentaries	Problem 6 : What is best yose play for Black ? Solution and commentaries

2. Snapbacks (utegaeshi)

Problem 1 : Black to play and kill Solution and commentaries

Problem 2 : Black to play and kill Solution and commentaries

Problem 3 : Black to play and kill Solution and commentaries

Problem 4 : Black to play and live   Solution and commentaries

Problem 5 : White to play and live Solution and commentaries

Problem 6 : Black to play and live Solution and commentaries

Problem 7 : Black to play and live    Solution et commentaires

Problem 8 : Black to play ; status ?   Solution and commentaries

Problem 9 : Black to play and save the marked stones Solution and commentaries

3. Under the stones (ishinoshita)

Example 1 : Black to play and live  Solution and commentaries

Example 2 : Black to play and live    Solution and commentaries

Example 3 : Black to play and kill Solution and commentaries

Problème 4 : Black to play and live  Solution and commentaries

Problème 5 : Black to play and kill   Solution and commentaries

Position 6 (a natural one) : what is White's best yose (and how much is it worth)? Solution and commentaries

Problem 7 : Black to play and kill by ko  Solution and commentaries		Problem 8 : Black to play and live unconditionally    Solution and commentaries		Problème 9 : White to play and live Solution and commentaries
Problem 10 (highly artificial) : Black to play ; status ? Solution and commentaries		Problem 11 (from a real game ?) : how could White afford to ignore the ko threat ? Solution and commentaries

Example 12 : Black to play and live  Solution and commentaries Problem 13 : Black to play ; status ? Solution and commentaries

4. Eye reduction (nakade)

Problem 1 : Black to play, status ? Solution and commentaries

Problem 2 : Black to play, status ? Solution and commentaries

Problem 3 : Black to play, status ? Solution and commentaries

Problem 4 : Black to play and kill (without ko). Solution and commentaries

Problem 5 : White to play, status?    Solution and commentaries

Problem 6 : Black to play and live. Solution and commentaries

Problem 7 (variation) : White to play and kill. Solution and commentaries

Problem 8 : Black to play and kill (without ko). Solution and commentaries	Problem 9 : Black to play and kill. Solution and commentaries		Problem 10 : Black to play and kill. Solution and commentaries
Problem 11 : Black to play and kill. Solution and commentaries	Problem 12 : Black to play and kill. Solution and commentaries
Problem 12a : Black to play and kill every white stone. Solution and commentaries	Problem 12b : Black to play and kill every white stone. Solution and commentaries
Problem 13 : White to play and kill every black stone. Solution and commentaries	Problem 14 : White to play and kill every black stone. Solution and commentaries

5. Blind spots

(?) Problem 1 : White to play ; status ? Solution and commentaries	(?) Problem 2 (variant) : Black to play ; status ? Solution and commentaries
(?) Problem 3 : Black to play ; status ?   Solution and commentaries

6. Reference positions

Problem 1 : Black to play and kill without ko          Solution and commentaries

Problème 2 : Black to play ; status ?       Solution and commentaries

Problem 3 : Black to play and kill          Solution and commentaries	Problem 4 : Black to play and kill          Solution and commentaries
Problem 5 : Black to play ; status ? Solution and commentaries	Problem 6 : Black to play and kill the white stone Solution and commentaries

Problem 1 (empress of tsumego) :         White to play and kill by ko Solution and commentaries

Variant : the Japanese setting Solution and commentaries

Problem 2 (emperor of tsumego) : no other stones on the board ; White to play and kill. Solution and commentaries

An improved variant ? Solution and commentaries

The ultimate variant (?) : no other stones on the board ; Black to play and live Solution and commentaries

Problem 3 (a serious contender) : White to play; status?          Solution and commentaries

Problem 4 (Dosetsu's problem, the most difficult ever) : Black to play and win the game    Solution and commentaries

II. Paradoxical tesujis and strange manoeuvres.

1. First line moves

Figure 1 : Black played the monkey jump ; how to block, and how many points does Black score ? Solution and commentaries

Problem 2 : Black to play ; what is the best yose ? Solution and commentaries

Problem 3 : Black to play and kill Solution and commentaries

Problem 4 : Black to play ; status ? Solution and commentaries

Problem 5 : Black to play and save the marked stones Solution and commentaries
Problem 6 : Black to play and save his surrounded stones Solution and commentaries	Problem 7 : Black to play and capture the 4 white stones Solution and commentaries
Problem 8 : Black to play and live Solution and commentaries
Problem 9 : White to play and kill the NE group Solution and commentaries

2. Shortage of liberties (damezumari)

Figure 1 : Black to play and kill     Solution and commentaries

Figure 2 : Black to play and kill      Solution and commentaries

Problem 3 :          Black to play and capture the three corner stones Solution and commentaries

Figure 4 : Black to play and save the corner stones      Solution and commentaries	Figure 5 : Black to play and live Solution and commentaries
Problem 6 : Black to play and live     Solution and commentaries	Problem 7 : Black to play and live Solution and commentaries	Problem 8 : Black to play and live Solution and commentaries

Position 9 (a classical one) : Black to play and live (without ko)      Solution and commentaries

Problem 10 : Black to play and live Solution and commentaries

Problem 11 : Black to play and live Solution and commentaries

Example 12 : Black to play and live Solution and commentaries
Problem 13 : Black to play and live (or escape) Solution and commentaries	Problem 14 : Black to play and live (what is the use of the marked stone ?) Solution and commentaries

3. Off-limits moves and phantom go

Figure 1 : Black to play and cut      Solution and commentaries

Problem 2 : Black to play and escape efficiently Solution and commentaries

Figure 3 : How to punish the cut ?      Solution and commentaries

Figure 4 : Black to play and connect the marked stones Solution and commentaries

Figure 5 : White to play and capture the side Solution and commentaries

Problem 6 : after the figure 5 attack, how can Black escape ? Solution and commentaries

Problem 7 : Black to play, status ? Solution and commentaries		Problem 8 : Black to play and capture the marked stones Solution and commentaries
Problem 9 : Black to play and save the 6 stones on the side Solution and commentaries
Problem 10 : Black to play and live Solution and commentaries		Problem 11 : Black to play ; status ? Solution and commentaries

4. Impossible cuts (atekomi, warikomi, etc.)

Problem 1 :         Black to play and save his surrounded stones. Solution and commentaries

Problem 2 :         Black to play and cut part of the white group. Solution and commentaries

Problem 3 : Black to play and save the marked stones.      Solution and commentaries

         Problem 4 : Black to play and live or escape.
Solution and commentaries

Problem 5 : Black to play and capture the largest white string     
Solution and commentaries

Problem 6 : Black to play and live.  
Solution and commentaries

Figure 7 : Black to play and exploit white weaknesses.     
Solution and commentaries

Problem 8 : Black to play and live (and what happens then to the white group ?).
Solution and commentaries

Problem 9 : Black to play and save the marked stones.    
Solution and commentaries

5. Traps and variations of joseki

Position 1 : White to play. If he blocks (left of 15), he will capture the cutting stones. So what is Black's plan ?   
Solution and commentaries

Position 2 : Black 5 looks suspicious ; what must White do, and where is the trap ?     
Solution and commentaries

6. Extraordinary moves played in real games

Position 1 : how would White put an immediate end to this game ?     Solution and commentaries

Position 2 : what is the threat behind this move ? And how should Black answer ?      Solution and commentaries

Position 3 : Black to play and wake up the corner aji Solution and commentaries

Position 4 : Black to play ; status? Solution and commentaries

Position 5 (first moves of the most famous game in history) : what happens if Black plays the "natural" ko threat above 31?      Solution and commentaries

Position 6 (later in the game) : now, what was Black answer to White attack at 126 ?     Solution and commentaries III. Ladders and other incredible sequences. Problem 1 : Black to play and put the marked stones to best use Solution and commentaries             Problem 2 : Black to play and awaken the aji of the marked stone Solution and commentaries             Problem 3 : Black to play and force White (O Meien) to resign     Solution and commentaries Problem 4 : White to play and live with the SE group     Solution and commentaries Problem 5 : Black to play and capture the marked stones     Solution and commentaries Problem 6 : Black to play and make both groups on the south edge live Solution and commentaries          Problem 7 : Black to play and make both groups in NE and SW corners live     Solution and commentaries   Problem 8 : White to play and capture the marked stones    Solution and commentaries   Problem 9 : White to play and save the marked stones     Solution and commentaries   (?) Problem 10 : White to play ; what happens if he tries to save the south edge group ?     Solution and commentaries Problem 11 : White to play ; what is the result ?     Solution and commentaries IV. Semeais, sekis and pseudo-sekis Figure 1 : who wins the semai?  Solution and commentaries   Figure 2 : White to play ; who wins the semai? Solution and commentaries Figure 3 : what is the result of the fight ? Solution and commentaries Figure 3bis : what is the result of the fight ? Solution and commentaries Figure 4 : what is the result of the fight ? Solution and commentaries   Semeai 5 : Black to play and win the race Solution and commentaries Semeai 6 : Black to play and win the game Solutions and commentaries Semeai 7 : what is the winning strategy in this case? Figure 8 : a well-known seki, but how is it scored ? Solution and commentaries Figure 9 : what say the rules ? Solution and commentaries Figure 10 : what is the result ? Solution and commentaries Figure 11 : what is the difference with the previous position ? Solution and commentaries Figure 12 : and what is the result in this case ? Solution and commentaries Figure 13 : an asymmetrical seki Solution and commentaries Figure 14 : what is the strange relation between those three positions? Solution and commentaries Figure 15 : sekis or false sekis ? Solution and commentaries Figure 16 : what is the result ? Solution and commentaries Figure 17 : what say the rules? Solution and commentaries Figure 18 : what say the rules?    Solution and commentaries Figure 19 : how must the fight be played ? Solution and commentaries Figure 20 : what is the result of the fight ? Solution and commentaries Figure 21 : what is the difference with the previous one ? Solution and commentaries Figure 22 : is this really a complete seki ? Solution and commentaries          (?) Figure 23 : Circular hanezeki ; what happens ? Solution and commentaries   V. Problems about rules.     Reference figure 1: "bent four in the corner" ; why is Black dead ? Solution and commentaries    Figure 2 :  bent four, with an unremovable ko threat ; what say the rules ? Solution and commentaries      Figure 3 : "generalized" bent four ; what say the rules ? Solution and commentaries   Figure 4 : How many points for Black ? Solution and commentaries Figure 5 : are the 4 white stones in the corner really dead ? Solution and commentaries The following positions illustrate relatively common superko situations (see here for solutions and commentaries) Exemple 6 : semeai with triple ko         Exemple 7 : simple ko with active seki         Exemple 8 : "round robin ko"         Exemple 9 : phoenix (chosei)    Figure 10 : is the NW group really alive in seki ? Solution and commentaries Figure 11 : Black to play ; how will the game continue ? Solution and commentaries Position 12 : self-captures allowed ; what does this change ? Solution and commentaries Curiosity 13 : It's White turn. Black retracts her last move, then lives Solution and commentaries         Curiosity 14 : Black to play and die Solution and commentaries         Variant 15 : self-capture allowed ; Black to play and live Solution and commentaries (?) Curiosity 16 : White to play and save the black stones in the SW corner (and who wins the game then ?) Solution and commentaries

Curiosity 17 ("unfair go") : White is allowed to play twice after every black move. Who wins the game ? Solution and commentaries