This is the "Etch-A-Sketch" project from The Odin Project.
To use this sketching program, you may go to this link
Or you can download the repo and simply open the index.html file.
Clicking the 'reset' button will allow you to generate a new grid. It'll ask you for an integer and then construct a grid with n*n dimensions. For instance, giving an integer value of 3 will result in a 3x3 grid.
The "Opacity" button will also request a grid size. Mousing over grids here will reduce the opacity of grids by 0.1.