This bouncy balls animation for Sketch sprinkles dots of random sizes and hues around your artboard using a ‘multiply’ blending mode, then bounces them off the artboard edges until you use the simple controls to the right of your artboard: Select the Yellow square to pause or the Red square to stop the demo and kill the loop entirely. If Sketch crashes try increasing the amount of time per frame—which is set in the scheduleWithRepeatingInterval_jsFunction() function. Just for reference I cobbled this together whilst blasting The Boys Next Door’s cover of These Boots Are Made For Walkin’ (1978).
Sketch plugins are written in CocoaScript which is basically JavaScript with access to Cocoa frameworks and a splash of that sassy Objective C bracket syntax. Just double-click the plugin file to install it.