Num Sum - C Version

A simple puzzle game that I made in my own custom C game framework. Now ported to a web build through emscripten. 
Repo Link: NumSum Repo

To summarize the goal and instructions:
Your objective is to mark all of the numbers that are valid in the grid.
A number is valid (it belongs on the grid) if it is part of a sum.
At the top of each column and at the side of each row is a sum for the entire column/row.
Your job is to piece together which numbers belong and which do not.
Mark the correct numbers and watch the sums go down.
When all of the valid numbers are marked you win.
More info in-game.