My favourite of these is Daniel Shiffman’s Coding Train Youtube videos. Dan is an incredibly enthusiastic and energetic teacher of coding, with his own unique style. He’s produced hundreds of freely-available videos on a whole host of programming topics.
So, taking inspiration from Dan’s videos I developed a simple sketch (below) in which the fish/jellyfish/stars (I can’t make up my mind what they are) interact with each other (they’re repelled, with the repulsion being proportionate to their size), and interact with the mouse when it hovers over the sketch. (They repelled by it too. Who knew that fish/jellyfish/stars don’t like mice?)