With that in mind, my last assignment was a problem, it was too addictive. An example of what it looked like:
Link to the applet here
Left Click: Attract all particles towards the cursor.
Left Click + Shift: Attract particles that are near the cursor to the cursor.
Right Click: Create a node at the cursor.
Right Click + Drag: Attract the primary node to the cursor.
Right Click + Shift: Create a secondary node at the cursor.
Middle Mouse Button: Deactivate all nodes.
Middle Mouse Button + Shift: Deactivate whatever node the mouse cursor over.
Have fun, it's addictive.