The Stripy Sudoku Solver

This solver is tentative while I figure out how to make this variant. For some reason I can't fathom yet the usual code to fill a board prior to making a puzzle simple won't fill. I'm hoping it's a simple code issue but will be interesting if it is a special property of the puzzle. So only one example I can give. But you can try subtracting clues to make a harder puzzle. Take the grade with a pinch of salt.

Stripy is the same puzzle as normal Sudoku but with an extra constraint. In a similar way to the rows, columns an boxes, the stripes must also be uniquely 1 to 9. All Sudoku strategies continue to apply - except the ones that rely on the deadly pattern used by Uniqueness strategies.

All feedback, comments, arguments, bug reports and strategy ideas are welcome. There is a new FEEDBACK form with a column displaying comments and questions. Many thanks to all the people who have done so and helped improve this solver.

Solver help

Use the "Import a Sudoku" button or type in a Sudoku puzzle in the small board.
You can also pick examples from the list above. Click on Take Step to step through the solution. Unknown squares are filled with 'candidates' - possible solutions.
Any cells that are reduced to one possible candidate are solved.