Adjusting Lightness value changes palette appearance. Moving cursor over the palette changes Hue and Saturation values. You can also enter numbers directly or use sliders. Constraint value allows choosing between perfect and restrained palette. Scale allows resizing palette, but bigger size doesn't add more precision and may cause lags.
Note: currently only Chrome and Firefox support WebGL 2.0. Edge will support it once it switches to Blink engine. Safari apparently has no plans to support it in the nearest future. If you're using an unsupported browser, you can still use numeric controls, you just won't be able to pick colors from the palette.
Visit project on GitHub.