pie
A guided breathing animation is presented as a segmented donut chart, with four colored arcs representing a cycle of inhale, hold, exhale, and hold phases. An animated gray overlay sweeps across the arcs to indicate the current phase, while a text label updates to show the active step. Built with D3 v6 and SVG, the code uses `d3.arc` to define arc shapes and `transition.attrTween` to animate the overlay’s angle. The duration of each phase is fixed, and the sequence repeats for a set number of cycles before stopping.