Bubble sort is a simple algorithm and offcourse in a real-live scenario you won't implement this using a visual programming environment... however, it's a nice test-case to help building a visual programming environment because it needs to be able to modify an array amongst other things.. So I've introduced the concept of being able to send commands to an array-node. When items are swapped, this is visualized by the array-node with some borders flashing and changing colors around the items that are being swapped. .. furthermore the array is iterated using a foreach-node which triggers a sub-flow for each array item.