Free to playScreenshots
From the Steam store
This is a sudoku game in different board sizes and difficulty. It also has an Editor mode that allows the user to create their own custom puzzles, custom layouts, and custom initial patterns, all of whom can then be played in Game mode. Furthermore, the customized items can also be shared, though it involves actually copying files from the user directory -- there is a button on the specific board mode so you can open that folder in explorer if you'd like to do this.
The trailer shows off most of these features, including most of the Editor-related ones.
