Platon Sudoku · Sudoku Study
Fish base lines · Core Concepts
Base lines are the rows or columns chosen to inspect every candidate of one digit. The blue rows are the starting point: each must eventually contain a 2; in the column version, start from the blue columns.
This course is adapted from Platon Sudoku App. Read the complete example here, then continue learning and practising in the app.
View on Google PlayDefinition
Base lines are the rows or columns chosen to inspect every candidate of one digit. The blue rows are the starting point: each must eventually contain a 2; in the column version, start from the blue columns.
How to find it
Focus on 2 and find every 2 in each of the two or three blue lines.
Common mistake
Blue marks the starting lines, not a completed fish. Next check which crossing lines contain their candidates.
X-Wing · Row
Teaching board · local candidate diagram
Observe candidates
Look only at candidate 2, at r2c2, r2c8, r6c2, r6c8; the line names can wait.
Verify the condition
Start from the blue row 2, row 6 and find every 2; each line must eventually contain one 2. These selected starting lines are the bases.
Draw the conclusion
The blue row 2, row 6 are the starting lines; every 2 on each is shown.
X-Wing · Column
Teaching board · local candidate diagram
Observe candidates
Look only at candidate 2, at r2c2, r8c2, r2c6, r8c6; the line names can wait.
Verify the condition
Start from the blue column 2, column 6 and find every 2; each line must eventually contain one 2. These selected starting lines are the bases.
Draw the conclusion
The blue column 2, column 6 are the starting lines; every 2 on each is shown.
Swordfish · Row
Teaching board · local candidate diagram
Observe candidates
Look only at candidate 2, at r2c2, r2c5, r5c5, r5c8, r8c2, r8c8; the line names can wait.
Verify the condition
Start from the blue row 2, row 5, row 8 and find every 2; each line must eventually contain one 2. These selected starting lines are the bases.
Draw the conclusion
The blue row 2, row 5, row 8 are the starting lines; every 2 on each is shown.
Swordfish · Column
Teaching board · local candidate diagram
Observe candidates
Look only at candidate 2, at r2c2, r5c2, r5c5, r8c5, r2c8, r8c8; the line names can wait.
Verify the condition
Start from the blue column 2, column 5, column 8 and find every 2; each line must eventually contain one 2. These selected starting lines are the bases.
Draw the conclusion
The blue column 2, column 5, column 8 are the starting lines; every 2 on each is shown.
Recognition practice
Teaching board · local candidate diagram
Recognition practice 1
Do all blue-base candidates lie on the marked cover lines?
Draw the conclusion
Yes
Recognition practice 2
Do all blue-base candidates lie on the marked cover lines?
Draw the conclusion
No
Recognition practice 3
Do all blue-base candidates lie on the marked cover lines?
Draw the conclusion
Yes
Recognition practice 4
Do all blue-base candidates lie on the marked cover lines?
Draw the conclusion
No
Recognition practice 5
Do all blue-base candidates lie on the marked cover lines?
Draw the conclusion
Yes
Recognition practice 6
Do all blue-base candidates lie on the marked cover lines?
Draw the conclusion
No
Recognition practice 7
Do all blue-base candidates lie on the marked cover lines?
Draw the conclusion
Yes
Recognition practice 8
Do all blue-base candidates lie on the marked cover lines?
Draw the conclusion
No
Recognition practice 9
Do all blue-base candidates lie on the marked cover lines?
Draw the conclusion
Yes
Recognition practice 10
Do all blue-base candidates lie on the marked cover lines?
Draw the conclusion
No
Recognition practice 11
Do all blue-base candidates lie on the marked cover lines?
Draw the conclusion
Yes
Recognition practice 12
Do all blue-base candidates lie on the marked cover lines?
Draw the conclusion
No
Practice
This course is adapted from Platon Sudoku App. Read the complete example here, then continue learning and practising in the app.
View on Google Play