A cat sitting in a regular square (l) and the Kanizsa square illusion (r). (Smith et al., Applied Animal Behaviour Science 2021) Our feline friends certainly wow us with their cleverness - they can fetch things, open doors, navigate seemingly impossible obstacles, and even understand basic instructions (when they feel like it, anyway). At other times, they can be hilariously silly. Any cat lover is familiar with their quirks, such as seemingly endless joy at knocking things off tables, and an innate fondness for sitting in enclosed spaces. The latter can apply even if that space is just a two-dimensional...