Well, loop through your projects and then create an input of type radio or a button for each project with the markup required by isotope (probably a data attribute). The rest should then be handled by isotope.
I think I was doing something wrong, it’s working properly now.
Except when I use <?php echo $category->category() ?> in the foreach loop, I get as result the name of the field, not it’s label for example: optionOne when I should get Option One from the blue print:
category:
label: Category
type: radio
options:
optionOne: Option One
“Option One” is just shown to the user in the Panel, while “optionOne” is what is saved in the content file. If you want to print “Option One” in the browser, you best create a “category map” in your config.php.