Special patterns that help you finding the solution:

- The tube
- The mirror
- The magnifyer
- The manifold
- Four-in-hand
- Three empty cells
- Four empty cells
- Hidden talent

The tube

Three empty cell in line function a a triple spotlight, in this exmaple for 1, 2 and 7. That results immediatley in sudoku for the marked cell... which one? 

  3  
  5
  
2 9  
9 5  4
    1
  8 7
← ← ←
9 8 3
4 5 6

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The mirror

A double tube can function as a mirror for a spotlight. That results in sudoku (3) for the marked cell.

5 6 8
← ← ←
→ → →
! 9 2
    6
  1 5
7    
5
 3
  
2
 6
 8

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The magnifyer

  A double tube can also broaden the beam of a spotlight...

! 9 2
    6
  1 5
5 6 8
← ← ←
← ← ←
7    
5
 3
  
2
 6
 8

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The manifold

When tubes cross, they function as a manifold: they divide a spotlight into thee beams.

     
3     
     
8  ↑ 2 
→ → →
 5 ↓  7
     
     
     

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Four-in-hand

When two identical duo's are in line (in this case 3), they control the area in between. That is why the marked cells also get a duo (3).

9   2
3    
3 4  
  7  
     
  8 2
  1 4
  3 2
7 3  

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Three empty cells

Look for three empty cells in a row, a column or a ninesome. Take a row as an example:

     
7    
     
7   2
  9  
     
     
1 2 5
4 7  
     
  3 9
  4  
3   4
  6 7
    9
6 9 7
  4 2
5   3
3    
     
     
9 7 1
     
  5  
     
7    
    4

In this row the candidates 1, 5 and 8 still must find a place. Two of these (1 en 5) can possibly be placed in exactly two cells (like two duo's). Therefore, the remaining 8 must belong in the other cell!

     
1
5		 3 9
  4  
3   4
1
5		 6 7
    9
6 9 7
8 4 2
5   3

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Four empty cells

Look for four empty cells in a row, a column or a ninesome. Take a row as an example: 

  3  
8 5
  
 2 9  
9 5  4
    1
   8  
  8  
9    
  5  6

In this row the candidates 1, 3, 4 and 7 still must find a place. Two of these (1 en 4) can possibly be placed in exactly two cells (like two duo's). Therefore, the remaining 3 and 7 must belong in the other two cells!

  3  
8 5
  
2 9 1
4
9 5  4
    1
3
7		  8 3
7
  8  
9    
1
4		 5  6

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Hidden talent

Combining rows and columns. Look for a cell in which only one candidate can be put: look for hidden talents on the crossroads of a crowded row and a crowded column. In the example, 6 is the only candidate in row ánd column. Just try all other candidates for this cell...

3 7  
    2
5 !  
  1 2
  4 6
9 7 3
9 6  
     
  8  
2 4 3
7 5  
     
7 6 5
1 2  
4 3  
     
6 4 3
5 2 7
  1  
     
    7
2 5  
3 9  
6 8  
    6
4    
     

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