I need checkboxes in combine to act as an AND, not as an OR

I used to be a programmer but did not program for 15 years so I am pre-web. I spent the last 2 days learning HTML and CSS to put together this: https://www.visualdiaryguide.com/selector.html

The problem is when I check the boxes, I need the selections to reflect the combination of Art Forms and Styles, not a collection. For example, when I click 2D-Painting and Realism, white selections should be reduced not expanded.

It feels like I'd need to re-design this whole thing (which I am hoping is not the case). I don't really want to also learn JavaScript :(

Any suggestions would be appreciated. I am assuming you can see the HTML and CSS code from the website so I am not including them here.

I tried to combine IDs, etc but to no avail.

I am assuming you can see the HTML and CSS code from the website so I am not including them here. https://www.visualdiaryguide.com/selector.html