Personally, I really liked the concept of this game, solving a sudoku within a 3D space, which each cell being a node you place a number into. It reminds me of those Minecraft adventure maps that manage to make something seemingly impossible within the confines of Minecraft command block logic.
However... The execution is not really that great. Technically, the game is one (actually, two) mod thrown on top of Minetest Game, which causes a number of oddities such as having access to the entire sfinv inventory, complete with grabbing items from the creative menu (yeah so about Minecraft adventure maps...). The nodes that make up the world are... new nodes, with existing but retextured textures, and the hotbar texture is the MTG 8-slot hotbar even though it's actually 9. Other than these things, the game doesn't make any use of MTG, and is just unnecessary bloat.
There is also a somewhat strange way of handling level completion. When you believe you have finished the sudoku, you need to punch the "Finisch" node and it will then verify to check if your sudoku is complete. Thing is... you can't make a wrong move, and you get all the necessary numbers in your hotbar, so a level completion check should be as easy as simple as checking that the player's inventory is empty, which could be done on every node placement at little cost.
I could go on about other things like how it spews messages into chat, there's no sound or any other kind of feedback when you make a wrong move or win a level, the levels are stored as tiny separate files in the sudoku mod, and that it uses the world folder's filesystem as a wacky key-value store (admittedly this game originally predates mod storage, but it's been updated since then...), but I'm afraid it might get petty.
The game hasn't seen an update in a long time, and isn't supported by Minetest versions newer than 5.4. However, I still love the game as a concept and wanted to see it in a better state than currently, so as such I took it upon myself and forked the game in Spring of 2022 to fix up many of these issues, add music and sounds, and in general improve it.
I released a new version of this Game yesterday.
The Slot hotbar is now fixerd. I also removed every Minetest Game mod.
Levels are now completed automatically and this Game also works with newer Versions of Minetest.
Sound are not added yet but I will think about it.
I will try to work more on this project in the future.