You have a README which is great, but you'll need a License file as well (these are two main criteria for open source category). Also change the name of your README file to the name of your project/game, and add some screenshots of your game to spice it up a little.

Full window on run is great, nice work. Add some sound effects and music too. Sometimes I'd click on a number and it wouldn't add it to the square, and other times it would, with no consistency or indication or why something is or isn't adding to the block. And sometimes clicking the number would remove another number instead. Is that a glitch?

Graphics are lovely and clean. Nice work on your submission.

Simple, but nice game. As others have pointed out, it's missing sound (at least some simple click effects) and I’d make level progression less linear. For example, after a couple of initial levels, unlock the next block with new operations, and let the player choose so they can continue here or start another block

Simple yet interesting, UI was clean and nice. Unfortunately no audio. Nicely done 👌

Cool game, but progression into different math functions is a bit slow. It would definitely improve with some audio as well. As it is, it is quite well laid out and functional though!

I love the clean UI. Nice, straightforward concept that you can easily build off of. My only wish is that I would have preferred to pick and choose which levels to play in case I wanted to jump ahead to the harder levels. Great job!

Overall, a fun simple puzzle game! It would great to add in a simple tutorial with instructions if time allowed.