Xuanxuan Qijing problems with solutions explained

Go problems from the Xuanxuan Qijing (玄玄棋经, Gengen Gokyo), the classic life-and-death collection of 1347, each with a diagram and the solution explained move by move.

Problem 1: White to play and escapeA lone white stone sits inside a loose net of five black stones. The quiet extension to K10 breaks the net whichever side Black blocks.
Problem 2: White to play and liveThree white stones on the second line have no room for eyes. The clamp at F18, on the far side of Black's blocking stone, saves them.
Problem 4: Black to play and killWhite's corner looks like it has room for two eyes along the top edge. The placement at A18 and a push at B18 leave White short of liberties.
Problem 5: White to play and liveWhite's stones in the corner have no eyes of their own, but Black's corner stones are thin. The cut at C16 lets White live without a ko.
Problem 6: Black to play and killBlack's two corner stones cannot escape, but they can be given up in the right shape. B19 is the key point: White captures a bulky five and dies.
Problem 7: Black to play and killWhite has one eye in the corner and wants a second in the centre. Black's placement at E16 takes it away before White can make it.
Problem 8: White to play and live in sekiWhite's stones are sealed in on the second line with a black stone already inside. Two eyes are out of reach, but A18 leads to seki.
Problem 9: White to play and killWhite's inside group and Black's surrounding wall are both short of eyes. Each side plays under the stones once, and White's comes last.
Problem 10: Black to play: ko or killBlack ataris at D18, descends to C19 and plays F15. White's best defence is a ko; the other defence loses to an under-the-stones sacrifice.
Problem 11: Black to play and killKnown as 'Beautifully Managed' (妙持). White has one eye in the corner and wants a second on the top edge. Black's hane at D19 and a cut at C18 take it away.
Problem 12: Black to play and win the capturing raceBlack's three stones on the edge and White's corner stones are racing to capture each other. The cut at G18 costs White a move, and Black wins by one.
Problem 13: White to play and make a koKnown as 'Old Hermit Refining the Pills of Immortality'. White cannot live outright, but B17 and the throw-in at A18 lead to a two-stage ko.
Problem 14: White to play and make a koBlack's corner looks roomy, but the placement at A18 and the atari at A16 turn it into a ko. Every other first move lets Black live.
Problem 15: Black to play and killWhite's corner looks big enough to live. The throw-in at D18 and the placement at A18 reduce it to a bent four in the corner, which is dead.
Problem 16: Black to play and killWhite's eye space lies along the top edge. Black plays in the middle of it at E19, and a shortage of liberties stops White from approaching on either side.
Problem 17: Black to play and surviveBlack is short of eye space, and the natural moves all fail. D19 leads to eternal life: a position that repeats, so White cannot kill.
Problem 18: White to play and make a koBlack's corner is close to alive. White's A18 and E19 squeeze it from both sides, and the best Black can do is a ko.
Problem 19: White to play and killBlack's eye space runs along the top edge. White narrows it from both ends, plays inside at D17, and uses an atari to take the last vital point.
Problem 20: Black to play and win the capturing raceTwo black stones race against two white ones. After extending to G18, Black's first-line move at E19 is a famous tesuji that wins the race by one move.
Problem 21: White to play and killKnown as 'Unstable Behavior' (德二三). White's first-line hane at F19 and a two-stone sacrifice split Black's corner from the top, and neither part lives.
Problem 22: White to play and make a koKnown as 'Battle of Wits' (鬥智). White's group lacks eye space, but the sacrifice cut at C17 makes enough trouble in the corner to get a ko.
Problem 23: White to play and make a koBlack's corner is one move from life. White's placement on the 1-2 point at A18 turns it into a ko; the direct push at B18 lets Black live.
Problem 24: Black to play and make a koBlack's group cannot make two eyes on the side. A18, the 1-2 point in the corner, gets a ko against White's best defence and outright life against the other.
Problem 26: Black to play and liveKnown as 四門斗底勢, after a battle formation in the novel Fengshen Yanyi. Black sacrifices two stones to squeeze White in the corner, then lives by not playing the usual throw-in.
Problem 27: Black to play and killKnown as 'Trapped Dragon' (困龍). A large white group has to live in the corner, and Black takes its eye space away from the first line on both sides.
Problem 29: Black to play and make a koKnown as 'A Fierce Tiger Throws Himself into the Forest' (猛虎投林). Black's edge sacrifice at A16 turns the capturing race in the corner into a ko, and wins it outright if White defends weakly.
Problem 30: White to play and liveKnown as 'Strange and Farseeing' (奇遠). White's scattered stones look lost, but B15 and the corner tesuji at A18 leave two follow-ups that Black cannot both stop.
Problem 32: Black to play and killKnown as 'Fox Hit by Arrow' (野狐中箭), also titled 進講. Black sacrifices a stone at F19 and then drives through the middle, cutting the white group in half.
Problem 33: White to play and killKnown as 'A Bat' (仙鼠). White's first-line moves at A18 and B19 take away Black's eye space, and the stones White gives up on the edge do not give Black a second eye.
Problem 34: Black to play and killWhite needs a second eye on the top edge. The shape is symmetrical, and Black's placement on the point of symmetry at K19 stops the eye on both sides.
Problem 35: White to play and killKnown as 'Little Wire Net' (小鐵網勢). White sacrifices two stones on the first line, plays back in, and captures four stones in a way that leaves the rest of Black's group in atari.
Problem 37: White to play and make a koTitled 'Eight Dragons Ascend to Heaven' (八龍昇天勢). White's centre stones seem lost in a capturing race, but sacrifices on the first and second lines make Black short of liberties on both sides and force a ko.
Problem 38: Black to play and killWhite's group has a wide but thin eye space. Black's placement at F17 strikes its centre, and against each of White's three answers Black leaves it short of liberties or eye space.
Problem 39: Black to play and killTitled 'Meet at the Source from Left and Right' (左右逢源勢). Black's first-line move at G19 protects a cutting point and threatens two white groups at once, so one of them dies.
Problem 42: White to play and killKnown as 'Ambush from All Sides' (十面埋伏). White's first-line sacrifice at H19, followed by G17, takes Black's eye space apart. The obvious first move only gets a seki.
Problem 43: Black to play and make a koWhite's corner looks safe, but Black's sacrifice at A18 is a hidden resource. White's only defence leads to a ko, and capturing the stone loses the corner. The same position is Gokyo Shumyo Section 3, Problem 59.
Problem 49: Black to play and killTitled 'Nine Old Men Playing Easily' (九老優遊勢). White answers Black's attack with a squeeze that captures six stones, but Black plays back under the stones and the white group dies.
Problem 50: White to play and killWhite forces Black to defend on both sides and then plays F14, putting two black chains in atari at once. Black can capture, but is caught in a double snapback.
Problem 51: White to play and killBlack's corner has no outside liberties, so White can do better than a ko. The placement at A18, followed by B18, leaves Black with a dead shape.
Problem 52: Black to play and win the capturing raceTitled 'Song of Five Stones' (五子之歌). In a capturing race, Black's D19 and C18 make a shape with the largest possible number of liberties. It is a shape that comes up often in real games.
Problem 53: Black to play and killTitled 'Shen Kuai Cuts Off His Arm' (申噲斷臂勢). After a natural opening sequence, Black's D19, G19 and E16, played in exactly that order, leave White short of liberties and unable to connect out.
Problem 54: Black to play and make a koBlack's corner stones cannot live outright. A two-stone sacrifice on the first line, followed by a throw-in at B19, turns the corner into a ko.
Problem 55: White to play and liveWhite's group on the left looks short of eyes. White first takes liberties from Black's stones along the top with M17, L18 and L19, and then the vital point at F18 gives life, or seki if Black resists.
Problem 57: Black to play and make a koTitled 'Troubled Tiger Escapes Trap' (困虎脫穽勢). Black's surrounded group cannot live or escape outright, but H17 and the first-line move at K19 get a ko in which Black captures first.
Problem 58: Black to play and make a koTitled 'Moon Palace' (月宮勢). Black's placement at J18 and the surprising follow-up at L18 force a ko against White's best defence. White's other defences lose the whole group.
Problem 59: Black to play and killBlack's and White's stones are cut into each other in the corner. Black pushes in at B17 and then uses the first line at D19 to come out ahead.
Problem 60: White to play and killWhite's placement at D18 is the only move that kills. Black can capture four stones, but White plays back into the space and the group dies.
Problem 62: Black to play and killWhite needs a second eye on the top edge. Black's first-line placement at E19, followed by F18, leaves White with only a false eye there.
Problem 65: White to play and killWhite's first-line placement at H19 kills. Black has three plausible defences, and each fails to a different follow-up because of a shortage of liberties.
Problem 66: White to play and make a koWhite's centre stones are cut off. After G18, the first-line move at G19 is the key: Black's best defence gives a ko, and the other lets White connect out by capturing three stones.
Problem 67: Black to play and liveTitled 'Six Dragons Fly to the Sky' (六龍御天勢). After a natural start, Black's first-line tesuji at B19 gets life in seki, or life by double ko if White resists the other way.
Problem 69: White to play and killWhite's first-line placement at C19 kills where the obvious hane only gets a ko. The follow-ups at F19 and E17 leave Black unable to connect for lack of liberties.
Problem 70: Black to play and liveBlack's corner group needs a second eye. The tempting capture at A18 gives only a ko, while the quiet first-line descent at C19 lives outright.
Problem 72: White to play and make a koWhite's placement at D18, followed by C19 and B18, reduces Black's corner to a ko. If Black defends the wrong way, the corner dies outright.
Problem 74: Black to play and liveBlack's group on the top side lives with J19, a first-line move that puts K19 in atari and widens the eye space. Every White attempt after it fails.
Problem 75: White to play and make a koWhite attacks Black's loosely connected corner stones with the first-line placement at B19. With correct play from both sides the corner becomes a ko.
Problem 77: Black to play and win the capturing raceBlack's two cut-off stones on the top side are in a capturing race. Black sacrifices two stones starting with K18 to shorten the liberties of one white group, then wins the race against the other.
Problem 79: White to play and killBlack's group on the top side seems to have an eye on each side. White gives up two stones starting with E18, throws in again where they were captured, and repeats the idea on the right, so Black is left with one eye.
Problem 81: Black to play and killWhite's group on the top side is short of eye space. Black pushes in at E18 and lets three stones be captured, then plays back in the middle of the three points to kill.
Problem 82: Black to play and killWhite's group on the top side looks close to two eyes. Black's placement at G19 on the first line leaves White a choice between a snapback on the left and losing the eye on the right.
Problem 83: Black to play and killA black stone sits inside White's group on the top side. Stepping down diagonally to D19 kills, while the straight descent to E19 fails.
Problem 86: Black to play and killWhite has a wide eye space on the top side. Black starts with the hane at A17 and the placement at B19, then uses a throw-in at E18 to kill cleanly.
Problem 87: White to play and killBlack's group on the top side has one open eye space. White's placement at D18 is the only move that kills; White then connects on the first line and extends from the placement.
Problem 88: Black to play and liveBlack sacrifices a stone at G18 and crawls along the first line all the way to the corner. The point is the last move: Black makes an eye with A18 before capturing, because capturing first leaves only false eyes.
Problem 90: Black to play and connectThree black stones on the top side are cut off by a white wall. Black plays F19 on the first line and connects underneath, and the white stones in between cannot get away.
Problem 91: Black to play and killWhite's group on the top side is in two halves with a narrow space between them. Black wedges in at D18 and, by playing the moves in the right order, ends with a double snapback.
Problem 92: Black to play and win the capturing raceThree black stones and a chain of white stones cut each other off on the top side. Black cuts at G17 and then uses moves on the first line to stop White from gaining liberties, winning the capturing race.