A Braille clock displays the current time in six-digit Braille format, with each digit rendered as a 2x3 grid of raised dots on a tactile-style interface. The visualization uses D3.js v4 to generate SVG circles for the Braille cells and applies CSS transitions to toggle their lit or unlit states, driven by a recursive `tick()` function that updates every second. The code employs D3 selections and data binding to map hour, minute, and second values to the appropriate dot patterns, while SVG gradients and filter effects simulate a physical, embossed surface under ambient light.