This example shows a collapsible operation tree for electric vehicle modes, with color-coded nodes distinguishing normal and fault operation modes alongside their sub-modes. Users can click nodes to expand or collapse child branches, triggering animated transitions as nodes reposition. Built with D3 v5, the visualization uses `d3.tree` and `d3.hierarchy` for layout and `d3.linkHorizontal` for curved links, while `d3.zoom` enables panning and zooming. Nodes are rendered as SVG rectangles with labels, and data comes from a static JavaScript object defining the hierarchical structure.