A yellow circle face with animated eyebrows demonstrates D3 v4 transitions. The face is drawn with SVG circles, rectangles, and an arc-based mouth, centered via a transformed group. Eyebrows move up and down using chained `transition().duration(2000)` calls that toggle their vertical offset. The code uses D3's `select`, `arc`, and transition API on static SVG elements, with no data binding or force simulation.