Click/tap to create a point. Click and drag from one point to another to link them. Tap a point again to anchor/lock it in place. Press space or click the triangle button ("▶") to run the simulation. Tap the icon with the three horizontal lines ("≡") to view settings that you can change and 5 examples you can load. While the simulation is running, you can drag across the screen to interact with the points. Press the "x" key on your keyboard or tap the plus icon/x icon ("+" or "x") to toggle between creating points/lines and deleting them. To delete points/lines, just hover over them and click them. (You can also do this while the simulation is running)