How would I do this?

I'm trying to figure out the best way to do this, and hope someone can help my ailing brain :slight_smile:

I have three sections:

Film Category
Genre
Niche

I want my users to be able to search within those to find the listings which include the categories within them, so with categories, they would look a little like this:

Film Category
Shorts
Features
Trailers

Genre
Horror
Sci-Fi
Thriller

Niche
British
Buddhist
Children

From that, I'd like people to be able to select the categories they want within each of the sections so, for example, they may be looking for short British horror & sci-fi films. For that they would have selected shorts from the film category, horror & sci-fi from the genre & British from the niche. How would I code that in?

Also, they may want to do a search with no niche selected.

I think the problem comes when it should list horror or sci-fi, the posts in the item shown should not have to be both horror & sci-fi.

In the final one I put together, there will be about 40 genres, so quite a lot to play with.

Any ideas?