3D 3X3 Cube L(2,1) D(9,3,2,0,0,0)
Moderate
True 3 dimensional problem, albeit a very simple one. Each 3X3 square is one plane of a 3X3X3 cube. Consider the squares stacked on top of each other. There are 9 planes in this problem each of which is a 3X3 square which must have no repeating characters. A couple of the planes are highlighted in colour.

Backslash L(2,1) D(18,13,12,0,0,0)
Moderate
Must have unique characters in each row and column but the 3 by 3 boxes are replaced by backslashes. These wrap left to right and top to bottom so the overall geometry is a doughnut (torus)

Jigsaw L(2,1) D(23,10,9,0,0,0)
Moderate
As regular 9 by 9 but the normal 3X3 boxes are irregular shapes

People L(2,3) D(21,9,9,1,1,0)
Difficult
The shapes have “lumps” on each side to become quite irregular. They look to me like little people. This problem wraps top to bottom and side to side so the overall geometry is like a doughnut (torus).

Toroid H L(2,3) D(24,13,12,1,1,0)
Difficult
The normal 3X3 boxes are replaced by horizontal stripes (helices) which wrap around the problem. These stripes join the left side to the right side and the top to the bottom so that the overall geometry is a doughnut (torus).

3D 4X4 Cube L(3,1) D(27,5,4,0,0,0)
Moderate
True 3 dimensional problem. Each 4X4 square is one plane of a 4X4X4 cube. Consider the squares stacked on top of each other. There are 12 planes in this problem each of which is a 4X4 square which must have no repeating characters. Some of the planes are highlighted. There are 16 possible characters so I use a standard hexadecimal character set: 0,1,2,…,9,a,…,f.

Backslash L(2,1) D(19,6,6,0,0,0)
Moderate
Must have unique characters in each row and column but the 3 by 3 boxes are replaced by backslashes. These wrap left to right and top to bottom so the overall geometry is a doughnut (torus)

Jigsaw L(2,1) D(24,5,4,0,0,0)
Moderate
As regular 9 by 9 but the normal 3X3 boxes are irregular shapes

People L(2,3) D(21,14,14,1,1,0)
Difficult
The shapes have “lumps” on each side to become quite irregular. They look to me like little people. This problem wraps top to bottom and side to side so the overall geometry is like a doughnut (torus).

Toroid V L(2,3) D(22,9,8,1,1,0)
Difficult
The normal 3X3 boxes are replaced by vertical stripes (helices) which wrap around the problem. These stripes join the left side to the right side and the top to the bottom so that the overall geometry is a doughnut (torus).

3D 3X3 Cube L(2,1) D(9,3,2,0,0,0)
Moderate
True 3 dimensional problem, albeit a very simple one. Each 3X3 square is one plane of a 3X3X3 cube. Consider the squares stacked on top of each other. There are 9 planes in this problem each of which is a 3X3 square which must have no repeating characters. A couple of the planes are highlighted in colour.

Diamond L(2,2) D(23,13,12,1,0,0)
Difficult
Here the shapes are pushed over to become diamonds. This wraps side to side but not top to bottom.

Jigsaw L(2,1) D(23,6,6,0,0,0)
Moderate
As regular 9 by 9 but the normal 3X3 boxes are irregular shapes

People L(2,3) D(20,10,10,1,1,0)
Difficult
The shapes have “lumps” on each side to become quite irregular. They look to me like little people. This problem wraps top to bottom and side to side so the overall geometry is like a doughnut (torus).

Toroid H L(3,3) D(17,12,11,1,1,0)
Difficult
The normal 3X3 boxes are replaced by horizontal stripes (helices) which wrap around the problem. These stripes join the left side to the right side and the top to the bottom so that the overall geometry is a doughnut (torus).

3D 4X4 Cube L(3,1) D(27,5,4,0,0,0)
Moderate
True 3 dimensional problem. Each 4X4 square is one plane of a 4X4X4 cube. Consider the squares stacked on top of each other. There are 12 planes in this problem each of which is a 4X4 square which must have no repeating characters. Some of the planes are highlighted. There are 16 possible characters so I use a standard hexadecimal character set: 0,1,2,…,9,a,…,f.

Diamond L(2,2) D(26,11,10,1,0,0)
Difficult
Here the shapes are pushed over to become diamonds. This wraps side to side but not top to bottom.

Jigsaw L(2,1) D(22,9,8,0,0,0)
Moderate
As regular 9 by 9 but the normal 3X3 boxes are irregular shapes

Difficult
The shapes have “lumps” on each side to become quite irregular. They look to me like little people. This problem wraps top to bottom and side to side so the overall geometry is like a doughnut (torus).

Toroid V L(2,3) D(22,15,14,3,1,0)
Difficult
The normal 3X3 boxes are replaced by vertical stripes (helices) which wrap around the problem. These stripes join the left side to the right side and the top to the bottom so that the overall geometry is a doughnut (torus).