I've seen dogs & cat apps that follow the cursor around the screen, & I've seen aquarium screensavers, but I've never seen a fish swim around the screen following the cursor. Or a spider for that matter. & then there's the idea that if it's a spider that if you click on it you squish it & it restarts from a specified position. Or maybe by squishing it, it splits into 2 spiders, & then when those 2 spiders are squished they split as well & so on... 
