Sudoku Solver

I’ve started working on a website in SvelteKit for playing sudoku that will use the C code through web assembly to generate and solve sudoku puzzles.
It currently has:

• A 9x9 grid of squares
• A blue border to indicate which one you have selected
• Ability to edit inside the square
• Red border if putting a number in an element makes the sudoku invalid

I added basic random sudoku generation by creating a solved grid and removing random numbers from the grid. In the future I want to optimize this approach by making sure there is only one unique solution, so that the sudoku puzzles generated are more challenging to solve (for people and the program!). I was doing some research and found that I can adapt my solver for this by making it continue after one solution to see if there are two and returning a value if so.