Mastering Basic Corner Shapes



Mastering Basic Corner Shapes - Step-by-step is a book by Youngsun Yoon

Review by Robert Jasiek

General Specification

  • Title: Mastering Basic Corner Shapes - Step-by-step
  • Author: Young Sun Yoon
  • Publisher: Korea Baduk Association et al
  • Edition: 2022-12-25
  • Language: English
  • Price: EUR 0 (plus any commission or postage)
  • Contents: life and death
  • ISBN: none
  • Printing: good
  • Layout: good
  • Editing: intermediate to weak
  • Pages: 270
  • Size: 153mm x 224mm
  • Diagrams per Page on Average: 2
  • Method of Teaching: selected examples
  • Read when EGF: 7k - 1k
  • Subjective Rank Improvement: o
  • Subjective Topic Coverage: -
  • Subjective Aims' Achievement: +


The book Mastering Basic Corner Shapes - Step-by-step contains life and death problems, answer diagrams and accompanying text. Besides short introduction, diagram index and appendix, the main part comprises 50 chapters on 229 pages. 36 chapters contain the problems while 14 chapters refer to their joseki origins. In the former, every chapter has 4 problems and a brief summary. Subtracting one duplicate, there are 143 problems. Within each chapter, the difficulty increases from the first to the fourth problem typically with a position a few moves earlier. Apart from the appendix, there is no structured theory.

Problem Selection

The book claims to present basic corner shapes and this is mostly correct. Of course, no single book can cover all shapes. The curios omission, however, is the most frequent basic corner shape resulting from the 3-3 under 4-4 invasion. Otherwise, the author has selected the shapes well: they occur rather frequently and offer a decent variety of techniques. The selection differs from All About Life and Death and more basic life and death books so makes more shapes accessible to the English literature.


For the four problems of a chapter, there are altogether about half a dozen to a dozen answer diagrams with short commenting texts, which contains hardly any further variations. The diagrams show solutions, variations, failures, or sometimes additional analysis.

The author speaks of the most relevant sequences in the diagrams. Some of them are relevant indeed but the reader must not fall under the illusion of sufficient diagrams. The greatest weakness of the book is the missing variations. The reader must read about two or three times as many relevant variations as shown. As a related aspect, the author mentions visualisation, memorisation and neuroscience in the introduction and appendix but fails to explain tactical reading and its decision-making, which would also consider the missing variations. A reader knowing tactical reading and reading all relevant variations can, however, profit more from the book by overcoming the author's or publisher's desire of pretending easy teaching and prominent layout.


Some of the problems might also be suitable for 10k - 8k players but such readers face the difficulties of the missing variations and presumed knowledge, although the appendix, which introduces bent-4, 10000-year-ko and approach ko, might mitigate this a bit if read in between. A few problems have some variations of intermediate difficulty suitable for low dans but a dan would not read the whole book just for them or a basic type of ko previously neglected in other texts. Hence, the core readership is 7k - 1k. A dedicated low dan should not condemn the book though, as it is a reminder of what he should know but probably partially might be missing. A reader can first solve the problems and then consult the book again for memorisation.


Although the book must have undergone some proofreading, there are many minor mistakes of language or sometimes contents but they do not obstruct reading significantly. An accompanying leaf only lists a few of them. There are occasional relevant mistakes of contents, such as swapped diagrams, a suboptimal solution disregarding the endgame, a few terms on ko types and counting versus scoring used wrongly, and consequences of shapes in the appendix for rules application. A reader of a free book can easily forgive such but should not blindly trust everything.


The author has been enabled to create the book so that it can be free. However, it might not be easily available because reasonable postage cannot be offered everywhere these days. Therefore, you might have to await distribution at some large tournaments or possibly pay some commission to a retailer.


Mastering Basic Corner Shapes - Step-by-step is a welcome addition to the English literature offering suitable practice for problem solving but should show more relevant variations, include the most frequent class of shapes and receive better proofreading.

Mastering Basic Corner Shapes last edited by RobertJasiek on April 28, 2023 - 14:03
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