Pixel values refer to the working resolution. Edit mode: hold a line until it buzzes to add a node (keep dragging to place it); hold a node until it buzzes, then lift without moving to delete it; hold a pink dot the same way to cycle which two of its three branches flow through. Moving the finger after the buzz just drags the node. Paths are reordered automatically after every change. Tap an open end, then another end or a node, to join them.