## Solving custom Sudokus - sudoku-solver.ch

**TLDR**: I built sudoku-solver.ch to solve custom, special-type Sudokus - check it out if you need some help to solve one!

A while ago, I solved a Geocache which consisted of **26 custom Sudokus**, each one being unique. Most of them had additional constraints (and therefore less numbers already filled in), for example this one:

Each arrow indicates that the number in the field pointed to is one bigger than in the field where the arrow is coming from.

As I wrote in Coming back to old problems - Sudoku, the basic technique of constraint propagation and backtracking is fairly efficient and can be extended to include additional constraints, like sums, smaller/bigger than, exact difference, etc.

Using the same techniques but adding additional constraints, I built sudoku-solver.ch, which allows for many common constraints to be added to the board.

Some features:

**Sudoku X**: Two additional diagonal units**Hyper Sudoku**: Four additional units**Killer Sudoku**(Sum Sudoku): Regions of variable size must form sums**Nonomino**: No 3x3 block units, but 9 custom, irregular units instead**Odd-Even Sudoku**: Normal Sudoku with odd/even constraints**Greater/Less Than Sudoku**: Normal Sudoku with greater/less than constraints

I also learned a lot about Web workers and generating beautiful random colors on the way.

You can check out the Source code here: Github