This interactive collapsible tree visualization displays a Korean AI startup ecosystem, hierarchically organized from the root category "인공지능" through industry and field subcategories down to individual company names. The data is loaded from both a CSV file and JSON, with the tree structure built using `d3.hierarchy` and `d3.tree`. Users can click any node to expand or collapse its child branches, with smooth transitions animated by `transition.attrTween` and node repositioning via `d3.linkHorizontal`. The visualization is rendered as an SVG with zoom support, and node updates use enter, update, and exit selections to handle dynamic hierarchy changes.