This interactive scatterplot matrix visualizes an environmental dataset, with each cell showing the relationship between two variables such as age, income, and education. Users can brush across any axis to filter the data points, which hides or highlights circles across all cells simultaneously using a brush interaction implemented with `d3.brush`. The visualization is rendered as SVG using D3 v4 within a React framework, with axes scaled via `d3.scaleLinear` and colored by categorical country data. A legend identifies the three color-coded countries: China, Brazil, and USA.