wp-calypso/client/my-sites/plans/doughnut-chart/style.scss

.doughnut-chart__wrapper {

	// percentage (0 to 100)
	@property --percentage {
		syntax: "<number>";
		inherits: true;
		initial-value: 0;
	}
	--width: 80px;
	--line-width: 9px;
	--main-color: var(--color-accent);

	&.blue {
		--main-color: var(--studio-blue-60);
	}

	background-color: var(--color-surface);
	width: var(--width);
	aspect-ratio: 1;
	position: relative;
	display: inline-grid;
	margin: 15px 0;
	place-content: center;
	font-size: $font-title-medium;
	border-radius: 50%;
	box-shadow:
		inset 0 0 0 var(--line-width) color-mix(in srgb, var(--main-color) 10%, transparent),
		inset 0 0 0 10px var(--color-surface);

	&::before,
	&::after {
		content: "";
		position: absolute;
		border-radius: 50%;
	}

	&::before {
		inset: 0;
		background:
			radial-gradient(farthest-side, var(--main-color) 98%, transparent) top/var(--line-width) var(--line-width) no-repeat,
			conic-gradient(var(--main-color) calc(var(--percentage) * 1%), transparent 0);
		-webkit-mask: radial-gradient(farthest-side, transparent calc(99% - var(--line-width)), var(--studio-black) calc(100% - var(--line-width)));
		mask: radial-gradient(farthest-side, transparent calc(99% - var(--line-width)), var(--studio-black) calc(100% - var(--line-width)));
	}

	&::after {
		inset: calc(50% - var(--line-width) / 2);
		background: var(--main-color);
		transform: rotate(calc(var(--percentage) * 3.6deg)) translateY(calc(50% - var(--width) / 2));

		.rtl & {
			transform: rotate(calc(var(--percentage) * 3.6deg * -1)) translateY(calc(50% - var(--width) / 2));
		}
	}
}