Motion tutorials (#949)

* update tween exercise

* update spring tutorial

Author: Rich-Harris

apps/svelte.dev/content/tutorial/02-advanced-svelte/03-stores/01-introducing-stores/+assets/app-a/src/lib/App.svelte renamed to apps/svelte.dev/content/tutorial/02-advanced-svelte/01-advanced-reactivity/05-stores/+assets/app-a/src/lib/App.svelte

@@ -1,5 +1,5 @@
 ---
-title: Introducing stores
+title: Stores
 ---
 
 Prior to the introduction of runes in Svelte 5, stores were the idiomatic way to handle reactive state outside components. That's no longer the case, but you'll still encounter stores when using Svelte (including in SvelteKit, for now), so it's worth knowing how to use them.

apps/svelte.dev/content/tutorial/02-advanced-svelte/03-stores/01-introducing-stores/+assets/app-a/src/lib/Counter.svelte renamed to apps/svelte.dev/content/tutorial/02-advanced-svelte/01-advanced-reactivity/05-stores/+assets/app-a/src/lib/Counter.svelte

@@ -0,0 +1,32 @@
+<script>
+	let progress = $state(0);
+</script>
+
+<progress value={progress}></progress>
+
+<button onclick={() => (progress = 0)}>
+	0%
+</button>
+
+<button onclick={() => (progress = 0.25)}>
+	25%
+</button>
+
+<button onclick={() => (progress = 0.5)}>
+	50%
+</button>
+
+<button onclick={() => (progress = 0.75)}>
+	75%
+</button>
+
+<button onclick={() => (progress = 1)}>
+	100%
+</button>
+
+<style>
+	progress {
+		display: block;
+		width: 100%;
+	}
+</style>

apps/svelte.dev/content/tutorial/02-advanced-svelte/03-stores/01-introducing-stores/+assets/app-a/src/lib/shared.js renamed to apps/svelte.dev/content/tutorial/02-advanced-svelte/01-advanced-reactivity/05-stores/+assets/app-a/src/lib/shared.js

@@ -0,0 +1,38 @@
+<script>
+	import { Tween } from 'svelte/motion';
+	import { cubicOut } from 'svelte/easing';
+
+	let progress = new Tween(0, {
+		duration: 400,
+		easing: cubicOut
+	});
+</script>
+
+<progress value={progress.current}></progress>
+
+<button onclick={() => (progress.target = 0)}>
+	0%
+</button>
+
+<button onclick={() => (progress.target = 0.25)}>
+	25%
+</button>
+
+<button onclick={() => (progress.target = 0.5)}>
+	50%
+</button>
+
+<button onclick={() => (progress.target = 0.75)}>
+	75%
+</button>
+
+<button onclick={() => (progress.target = 1)}>
+	100%
+</button>
+
+<style>
+	progress {
+		display: block;
+		width: 100%;
+	}
+</style>

apps/svelte.dev/content/tutorial/02-advanced-svelte/03-stores/01-introducing-stores/+assets/app-b/src/lib/Counter.svelte renamed to apps/svelte.dev/content/tutorial/02-advanced-svelte/01-advanced-reactivity/05-stores/+assets/app-b/src/lib/Counter.svelte

@@ -2,28 +2,53 @@
 title: Tweened values
 ---
 
-Alongside the `writable` and `readable` stores, Svelte ships stores for adding motion to your user interfaces.
+Often, a good way to communicate that a value is changing is to use _motion_. Svelte ships classes for adding motion to your user interfaces.
 
-Let's start by changing the `progress` store to a `tweened` store:
+Import the `Tween` class from `svelte/motion`:
 
 ```svelte
 /// file: App.svelte
 <script>
-	import { +++tweened+++ } from 'svelte/+++motion+++';
+	+++import { Tween } from 'svelte/motion';+++
 
-	const progress = +++tweened+++(0);
+	let progress = $state(0);
 </script>
 ```
 
+Turn `progress` into an instance of `Tween`:
+
+```svelte
+/// file: App.svelte
+<script>
+	import { Tween } from 'svelte/motion';
+
+	let progress = +++new Tween+++(0);
+</script>
+```
+
+The `Tween` class has a writable `target` property and a readonly `current` property — update the `<progress>` element...
+
+```svelte
+<progress value={progress.+++current+++}></progress>
+```
+
+...and each of the event handlers:
+
+```svelte
+<button onclick={() => (progress.+++target+++ = 0)}>
+	0%
+</button>
+```
+
 Clicking the buttons causes the progress bar to animate to its new value. It's a bit robotic and unsatisfying though. We need to add an easing function:
 
 ```svelte
 /// file: App.svelte
 <script>
-	import { tweened } from 'svelte/motion';
+	import { Tween } from 'svelte/motion';
 	+++import { cubicOut } from 'svelte/easing';+++
 
-	const progress = tweened(0, +++{
+	let progress = new Tween(0, +++{
 		duration: 400,
 		easing: cubicOut
 	}+++);
@@ -32,11 +57,11 @@ Clicking the buttons causes the progress bar to animate to its new value. It's a
 
 > [!NOTE] The `svelte/easing` module contains the [Penner easing equations](https://web.archive.org/web/20190805215728/http://robertpenner.com/easing/), or you can supply your own `p => t` function where `p` and `t` are both values between 0 and 1.
 
-The full set of options available to `tweened`:
+The full set of options available to `Tween`:
 
 - `delay` — milliseconds before the tween starts
 - `duration` — either the duration of the tween in milliseconds, or a `(from, to) => milliseconds` function allowing you to (e.g.) specify longer tweens for larger changes in value
 - `easing` — a `p => t` function
 - `interpolate` — a custom `(from, to) => t => value` function for interpolating between arbitrary values. By default, Svelte will interpolate between numbers, dates, and identically-shaped arrays and objects (as long as they only contain numbers and dates or other valid arrays and objects). If you want to interpolate (for example) colour strings or transformation matrices, supply a custom interpolator
 
-You can also pass these options to `progress.set` and `progress.update` as a second argument, in which case they will override the defaults. The `set` and `update` methods both return a promise that resolves when the tween completes.
+You can also call `progress.set(value, options)` instead of assigning directly to `progress.target`, in which case `options` will override the defaults. The `set` method returns a promise that resolves when the tween completes.

apps/svelte.dev/content/tutorial/02-advanced-svelte/03-stores/01-introducing-stores/+assets/app-b/src/lib/shared.js renamed to apps/svelte.dev/content/tutorial/02-advanced-svelte/01-advanced-reactivity/05-stores/+assets/app-b/src/lib/shared.js

@@ -1,23 +1,21 @@
 <script>
-	import { writable } from 'svelte/store';
-
-	let coords = writable({ x: 50, y: 50 });
-	let size = writable(10);
+	let coords = $state({ x: 50, y: 50 });
+	let size = $state(10);
 </script>
 
 <svg
 	onmousemove={(e) => {
-		coords.set({ x: e.clientX, y: e.clientY });
+		coords = { x: e.clientX, y: e.clientY };
 	}}
-	onmousedown={() => size.set(30)}
-	onmouseup={() => size.set(10)}
+	onmousedown={() => (size = 30)}
+	onmouseup={() => (size = 10)}
 	role="presentation"
 >
 	<circle
-		cx={$coords.x}
-		cy={$coords.y}
-		r={$size}
-	/>
+		cx={coords.x}
+		cy={coords.y}
+		r={size}
+	></circle>
 </svg>
 
 <div class="controls">