Svelte 5 - Uncaught ReferenceError: $state is not defined

I am trying to make Svelte 5 project (I know it is still in alpha, but I want to play a bit with it), and I am using this as a template for now

My App.svelte

<script>    import { withPrevSignals } from './withPrev'    const color = withPrevSignals('green')    let inputVal = $state('')    function save() {        color.curr = inputVal;        inputVal = ''    }</script><p>Prev: {color.prev}</p><p>Curr: {color.curr}</p><input bind:value={inputVal} /><button on:click={save}>Save</button><button on:click={color.undo}>Undo</button>

withPrev.js

export function withPrevSignals(initialValue) {    let curr = $state(initialValue)    let prev = $state(undefined)    function undo() {        curr = prev        prev = undefined    }    return {        get curr() { return curr },        set curr(newValue) {            prev = curr            curr = newValue        },        get prev() { return prev },        undo    }}

I keep getting an Uncaught ReferenceError: $state is not defined both in the svelte 5 playground and on the local. What am I doing wrong here?