:host {
	--_color-green: var(--color-green, yellowgreen);
	--_color-yellow: var(--color-yellow, gold);
	--_color-orange: var(--color-orange, orange);
	--_color-red: var(--color-red, red);
	--_color-red-dark: var(--color-red-dark, #a00);
	--_color-invalid: var(--color-invalid, hsl(220 10% 60%));

	/* Low-level scales, i.e. between pairs of our core colors */
	--color-scale-1: color-mix(in oklch, var(--_color-green), var(--_color-yellow) var(--progress-1));
	--color-scale-2: color-mix(in oklch, var(--_color-yellow), var(--_color-orange) var(--progress-2));
	--color-scale-3: color-mix(in oklch, var(--_color-orange), var(--_color-red) var(--progress-3));

	/* Recursive scales: their only purpose is to select one of the low-level scales, and will only ever have 0%/100% positions
	   For N colors there are N-2 + N-3 + ... + 1 = (N-1)(N-2) / 2 of these
	*/
	--color-scale-12: color-mix(in oklch, var(--color-scale-1), var(--color-scale-2) var(--progress-12));
	--color-scale-23: color-mix(in oklch, var(--color-scale-2), var(--color-scale-3) var(--progress-23));
	--color-scale-123: color-mix(in oklch, var(--color-scale-12), var(--color-scale-23) var(--progress-123));

	--gamut-progress: calc(var(--gamut-level) / (var(--gamut-count) - 1));
	--progress-ext: calc(var(--gamut-progress) * 300%);

	--progress-123: clamp(0%, (var(--progress-ext) - 150%)       * infinity, 100%);
	--progress-12:  clamp(0%, (var(--progress-ext) - 150% + 75%) *  infinity, 100%);
	--progress-23:  clamp(0%, (var(--progress-ext) - 150% - 75%) * infinity, 100%);

	--progress-1:   clamp(0%, var(--progress-ext), 100%);
	--progress-2:   calc(clamp(100%, var(--progress-ext), 200%) - 100%);
	--progress-3:   calc(clamp(200%, var(--progress-ext), 300%) - 200%);

	--color-level-infinity: var(--_color-red-dark);
	--color: var(--color-scale-123, var(--_color-invalid));

	display: inline-flex;
	align-items: center;
	justify-content: center;
	border-radius: .2em;
	color: white;
	background-color: var(--color);
	font-weight: bold;
	padding-inline: .4em;
	line-height: 1.4;

	/* See https://lea.verou.me/blog/2024/contrast-color/ */
	--l: clamp(0, (l / var(--l-threshold, 0.7) - 1) * -infinity, 1);
	color: oklch(from var(--color) var(--l) 0 h);
}

:host([gamut="none"]) {
	background-color: var(--color-level-infinity);
}

#label {
	&::before {
		content: var(--gamut-label, "N/A");
	}

	@supports not (color: color(from red xyz-d65 y y y)) {
		/* https://miunau.com/posts/dynamic-text-contrast-in-css/ */
		filter: invert(1) grayscale(1) brightness(1.3) contrast(9000);
		mix-blend-mode: luminosity;
	}

	@supports (color: color(from red xyz-d65 y y y)) {
		/* https://lea.verou.me/blog/2024/contrast-color/ */
		--y-threshold: 0.36;
		--y: clamp(0, (var(--y-threshold) - y) * infinity, 1);

		color: color(from var(--color) xyz-d65 var(--y) var(--y) var(--y));
	}
}

@property --color {
	syntax: "<color>";
	inherits: true;
	initial-value: transparent;
}