Pinia is the official store for Vue 3 (replaces Vuex). Key differences:

	Vuex	Pinia
Mutations	Yes (required)	Don't exist
TypeScript	Limited support	Native support
Stores	Modules inside 1 store	Independent stores
Syntax	Options or Setup	Options or Setup
DevTools	Yes	Yes
Composition	Complex (namespaced modules)	Simple (import and use)

// Pinia store
import { defineStore } from 'pinia'
import { ref, computed } from 'vue'

export const useCartStore = defineStore('cart', () => {
  const items = ref<CartItem[]>([])
  const total = computed(() => items.value.reduce((sum, i) => sum + i.price, 0))

  function addItem(item: CartItem) {
    items.value.push(item)
  }

  return { items, total, addItem }
})