svelte/documentation/tutorial/09-motion/02-spring/text.md

title
Spring

The spring function is an alternative to tweened that often works better for values that are frequently changing.

In this example we have two stores — one representing the circle's coordinates, and one representing its size. Let's convert them to springs:

<script>
	import { spring } from 'svelte/motion';

	let coords = spring({ x: 50, y: 50 });
	let size = spring(10);
</script>

Both springs have default stiffness and damping values, which control the spring's, well... springiness. We can specify our own initial values:

let coords = spring(
	{ x: 50, y: 50 },
	{
		stiffness: 0.1,
		damping: 0.25
	}
);

Waggle your mouse around, and try dragging the sliders to get a feel for how they affect the spring's behaviour. Notice that you can adjust the values while the spring is still in motion.

Consult the API reference for more information.