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Collections are a way for you to organize kata so that you can create your own training routines. Every collection you create is public and automatically sharable with other warriors. After you have added a few kata to a collection you and others can train on the kata contained within the collection.
Get started now by creating a new collection.
Wait, does this work is there is only one zero somewhere in the grid ?
If you take one 9 and turn it into a 0 in the grid, 0 to 8 is still 9 numbers in the row, the column and the region.
I really like the approach though.