[x] When a user clicks the "Join Mission" button, action needs to be dispatched to update the store. You need to get the ID of the selected mission and update the state. Remember you mustn't mutate the state. Instead, you need to return a new state object with all missions, but the selected mission will have an extra key reserved with its value set to true. You could use a JS filter() or map() to set the value of the new state