diff --git a/src/app.css b/src/app.css
index 050af8c..c72999d 100644
--- a/src/app.css
+++ b/src/app.css
@@ -70,6 +70,25 @@ button.colored {
 	border-color: var(--accent-color);
 }
 
+.lds-dual-ring {
+	display: inline-block;
+}
+.lds-dual-ring:after {
+	content: " ";
+	display: inline-block;
+	width: 6px;
+	height: 6px;
+	margin: 0 0 0 8px;
+	border-radius: 50%;
+	border: 2px solid var(--accent-color);
+	border-color: var(--accent-color) transparent var(--accent-color) transparent;
+	animation: spin 1.2s linear infinite;
+}
+@keyframes spin {
+	0% { transform: rotate(0deg); }
+	100% { transform: rotate(360deg); }
+}
+
 button.colored:hover {
 	background-color: white;
 	font-weight: bold;
diff --git a/src/lib/QueryInput.svelte b/src/lib/QueryInput.svelte
index 1892363..3e43f23 100644
--- a/src/lib/QueryInput.svelte
+++ b/src/lib/QueryInput.svelte
@@ -7,19 +7,20 @@
 </script>
 
 <div class="query-input-header">
-    <div on:click={() => jsFilter = !jsFilter}>
+    <label>
         Use JavaScript to filter messages
         <input type=checkbox bind:checked={jsFilter}>
-    </div>
+    </label>
 </div>
 
 <div class={"query-input-display" + (big ? ' big' : '')}>
     {#if jsFilter}
         <div class="query-input-hideable" transition:slide|local>
-            <div title="If enabled, mutations made by the below code will be displayed in the result data.">
-                Allow JavaScript to mutate objects
+            <label title="If enabled, mutations made by the below code will be displayed in the result data."
+                 on:click={() => mutableObjects = !mutableObjects} >
+                Allow mutation of message data
                 <input type=checkbox bind:checked={mutableObjects}>
-            </div>
+            </label>
             <textarea class='query-input' bind:value={queryCode}></textarea>
         </div>
     {/if}
@@ -42,7 +43,7 @@
         margin-top: 1em;
         display: flex;
         flex-direction: column;
-        /* For some reason, using flex-grow: 1; broke the slide in transition */
+        /* For some reason, using flex-grow: 1; broke the slide-in transition */
         height: 100%;
     }
 
diff --git a/src/lib/constants.js b/src/lib/constants.js
index df1e712..77cf05b 100644
--- a/src/lib/constants.js
+++ b/src/lib/constants.js
@@ -6,6 +6,12 @@ export const queryMode = {
   KILL: 'kill'
 }
 
+export const queryState = {
+  LOADING: 'loading',
+  DONE: 'done',
+  IDLE: 'idle',
+}
+
 export const backendAddressAndPort = 'localhost:3000'
 
 export const backendUrl = `http://${backendAddressAndPort}`
diff --git a/src/lib/header/NavBar.svelte b/src/lib/header/NavBar.svelte
index b2f0f8e..b08ac3f 100644
--- a/src/lib/header/NavBar.svelte
+++ b/src/lib/header/NavBar.svelte
@@ -8,8 +8,13 @@
     </svg>
     <ul>
         <li class:active={$page.url.pathname === '/'}>
-            <a sveltekit:prefetch href="/">Message Search</a>
+            <a sveltekit:prefetch href="/">Topic Search</a>
         </li>
+        <!--
+        <li class:active={$page.url.pathname === '/post-message'}>
+            <a sveltekit:prefetch href="/post-message">Post Message</a>
+        </li>
+        -->
         <li class:active={$page.url.pathname === '/settings'}>
             <a sveltekit:prefetch href="/settings">Settings</a>
         </li>
diff --git a/src/lib/state.js b/src/lib/state.js
index 4da4efa..f7d8402 100644
--- a/src/lib/state.js
+++ b/src/lib/state.js
@@ -1,7 +1,7 @@
 // noinspection JSCheckFunctionSignatures
 
 import { writable } from 'svelte/store'
-import { backendAddressAndPort, queryMode } from './constants.js'
+import { backendAddressAndPort, queryMode, queryState } from './constants.js'
 
 const getRandomFromArray = array => array[Math.floor(Math.random() * array.length)]
 
@@ -16,21 +16,23 @@ const addMetadata = mockItem => ({
   key: null,
 })
 
-const mockItems = [
+const mockItems = () => [
   {
-    "eventType": "Television",
-    "broughtToYouBy": "AMC",
-    "title": "Breaking Bad"
+    eventType: "purchase",
+    userName: "sagev",
+    itemName: "Bean Enchilada",
+    quantity: getRandomFromArray([1, 2, 3])
   },
   {
-    "eventType": "Television",
-    "broughtToYouBy": "CBS",
-    "title": "Breaking Bad Bang Theory"
+    eventType: "purchase",
+    userName: "cameronl",
+    itemName: "Tacos",
+    quantity: getRandomFromArray([1, 2, 3])
   },
   {
-    "eventType": "Movie",
-    "broughtToYouBy": "20th Century Fox",
-    "title": "Star Wars 2: The Star Warsening, brought to you by the Big Stink Corporation, a division of PepsiCo and somehow also Disney."
+    eventType: "refund",
+    userName: "sagev",
+    purchaseId: crypto.randomUUID(),
   },
 ].map(addMetadata)
 
@@ -40,8 +42,11 @@ export const state = writable({
   items: [],
   itemCount: undefined,
   matchCount: undefined,
+  queryState: queryState.IDLE,
   error: 'Connecting to WebSocket...',
   errorDetails: undefined,
+  queryStartTime: undefined,
+  queryEndTime: undefined,
 })
 
 const updateClearError = updater => state.update(s => {
@@ -61,8 +66,12 @@ const testQuery = (mode) => {
   runTestQuery = true
   try {
     if (mode === queryMode.REAL_TIME) {
+      state.update(s => ({
+        ...s,
+        queryStartTime: new Date()
+      }))
       const addItem = () => {
-        const item = getRandomFromArray(mockItems)
+        const item = getRandomFromArray(mockItems())
         if (filterFunc(item, item.value, JSON.stringify(item))) {
           item.timestamp = new Date().getTime()
           state.update(s => ({
@@ -79,9 +88,16 @@ const testQuery = (mode) => {
     } else {
       state.update(s => ({
         ...s,
-        items: mockItems.filter(item => filterFunc(item, item.value, JSON.stringify(item))),
-        itemCount: (s.itemCount || 0) + 1
       }))
+      setTimeout(() => {
+        const items = mockItems().filter(item => filterFunc(item, item.value, JSON.stringify(item)))
+        state.update(s => ({
+          ...s,
+          items,
+          itemCount: items.length,
+          queryState: queryState.DONE
+        }))
+      }, testTimeout * 10)
     }
   } catch (e) {
     console.log('Caught an error:', e.toString())
@@ -90,9 +106,12 @@ const testQuery = (mode) => {
 }
 
 export const killQuery = async ({ }) => {
-  // TODO
   if (testMode) {
     runTestQuery = false
+    updateClearError(s => ({
+      ...s,
+      queryState: queryState.DONE
+    }))
     return
   }
   ws.send(JSON.stringify({
@@ -109,7 +128,13 @@ export const query = async ({ cluster, topic, mode, jsFilter, queryCode, maxItem
   }
   itemLimit = maxItems
 
-  updateClearError(s => ({ ...s, items: [], itemCount: 0 }))
+  updateClearError(s => ({
+    ...s,
+    items: [],
+    itemCount: 0,
+    queryState: queryState.LOADING,
+    queryStartTime: new Date()
+  }))
   if (testMode) {
     testQuery(mode)
     return
@@ -171,7 +196,8 @@ export const connect = () => {
         case 'complete':
           updateClearError(s => ({
             ...s,
-            items: data.message
+            items: data.message,
+            queryState: queryState.DONE
           }))
           break;
         case 'item_count':
diff --git a/src/routes/+page.js b/src/routes/+page.js
index 0ceb977..0d051e5 100644
--- a/src/routes/+page.js
+++ b/src/routes/+page.js
@@ -1,4 +1,4 @@
-import { apiFetch } from "../utils.js";
+import { apiFetch, setStateError } from "../utils.js";
 import { killQuery, query } from "../lib/state.js";
 
 export const getTopics = async cluster =>
@@ -48,12 +48,12 @@ export const getClusterNames = async () => Object.keys((await apiFetch('/cluster
 
 export const startQuery = querySettings => {
   localStorage.setItem('querySettings', JSON.stringify(querySettings))
-  query(querySettings)
-  return true
+  query(querySettings).catch(setStateError)
+  return querySettings.mode
 }
 
 export const stopQuery = querySettings => {
-  killQuery(querySettings)
+  killQuery(querySettings).catch(setStateError)
   return false
 }
 export const defaultQueryCode =
diff --git a/src/routes/+page.svelte b/src/routes/+page.svelte
index 4db9ccf..862facf 100644
--- a/src/routes/+page.svelte
+++ b/src/routes/+page.svelte
@@ -1,10 +1,10 @@
 <script>
 	import { onMount } from 'svelte'
-	import { slide, fly, scale } from 'svelte/transition'
+	import { slide, fade } from 'svelte/transition'
 	import { JsonView } from '@zerodevx/svelte-json-view'
 	import QueryInput from '$lib/QueryInput.svelte'
 	import { state, connect } from '$lib/state'
-	import { queryMode } from '../lib/constants.js'
+	import { queryMode, queryState } from '../lib/constants.js'
 	import Modal from '../lib/Modal.svelte';
 	import {
 		defaultQueryCode,
@@ -17,7 +17,7 @@
 	export let errors, data
 
 	let showQueryModal = false
-	let queryRunning = false
+	let queryRunning = ''
 
 	const fontSizes = [30, 50, 67, 80, 90, 100, 110, 120, 133, 150]
 	let jsonDisplay = {
@@ -44,9 +44,9 @@
 
 	let topics = []
 	let clusterNames = []
-	const updateTopics = async (updateTopic = true) => {
+	const updateTopics = async () => {
 		topics = await getTopics(querySettings.cluster)
-		if (updateTopic) {
+		if (!querySettings.topic || !topics.includes(querySettings.topic)) {
 			querySettings.topic = topics[0]
 		}
 	}
@@ -73,6 +73,9 @@
 
 		connect()
 		clusterNames = await getClusterNames()
+		if (!clusterNames.includes(querySettings.cluster)) {
+			querySettings.cluster = clusterNames[0]
+		}
 		await updateTopics()
 
 		// Reload with confirmed truthful values
@@ -93,12 +96,16 @@
 		<NavBar />
 		-->
 		<h1>Topic Search</h1>
-		{#if $state.error}
-			<div class="state-error">{$state.error}</div>
-			{#if $state.errorDetails}
-				<div class="state-error-details">{$state.errorDetails}</div>
+		<div class="state-error">
+			{#if $state.error}
+				<span transition:fade={{duration: 100}}>{$state.error}</span>
+				{#if $state.errorDetails}
+					<div class="state-error-details">{$state.errorDetails}</div>
+				{/if}
+			{:else}
+				&nbsp;
 			{/if}
-		{/if}
+		</div>
 
 		<div class="settings-option">
 			<h3>Cluster</h3>
@@ -132,7 +139,7 @@
 				bind:mutableObjects={querySettings.mutableObjects}
 				bind:queryCode={querySettings.queryCode} />
 			{#if querySettings.jsFilter}
-				<button class="query-input-button" on:click={() => showQueryModal = true}>Open Large Editor</button>
+				<button class="query-input-button" on:click={() => showQueryModal = true}>Open Editor Window</button>
 			{/if}
 			{#if showQueryModal}
 				<Modal onClickOut={() => showQueryModal = false}
@@ -174,18 +181,22 @@
 		-->
 
 		<div class="query-button">
-			{#if queryRunning}
-				<button transition:slide class="danger" on:click={() => queryRunning = stopQuery(querySettings)}>Stop Query</button>
+			{#if queryRunning && $state.queryState !== queryState.DONE}
+				<div transition:slide|local class="stop-button">
+					<button class="danger" on:click={() => queryRunning = stopQuery(querySettings)}>
+						{queryRunning === queryMode.REAL_TIME ? 'End Real Time' : 'Cancel One-Shot'} Query
+					</button>
+				</div>
 			{:else}
-				<button transition:scale class="colored"
-						on:click={() => queryRunning = startQuery({...querySettings, mode: queryMode.ONE_SHOT})}>
-					Start One-Shot
-				</button>
-				<div class="separator"></div>
-				<button transition:slide class="colored"
-						on:click={() => queryRunning = startQuery({...querySettings, mode: queryMode.REAL_TIME})}>
-					Start Real-Time
-				</button>
+				<div transition:slide|local class="start-buttons colored">
+					<button class="colored" on:click={() => queryRunning = startQuery({...querySettings, mode: queryMode.ONE_SHOT})}>
+						Start One-Shot
+					</button>
+					<div class="separator"></div>
+					<button class="colored" on:click={() => queryRunning = startQuery({...querySettings, mode: queryMode.REAL_TIME})}>
+						Start Real-Time
+					</button>
+				</div>
 			{/if}
 		</div>
 	</div>
@@ -206,6 +217,12 @@
 				{#if $state.itemCount >= 0}
 					<div class="data-view-results">
 						{$state.itemCount} Messages
+						<!-- TODO: Error indicator? -->
+						{#if $state.queryState === queryState.DONE}
+							<span style="color: green; font-weight: bold;">✓</span>
+						{:else if $state.queryState === queryState.LOADING}
+							<span class="lds-dual-ring"></span>
+						{/if}
 					</div>
 				{/if}
 				<div class="border-between zoom-buttons">
@@ -329,6 +346,11 @@
 		border-style: none;
 		/* New button CSS */
 		display: flex;
+		flex-direction: column;
+	}
+	.start-buttons, .stop-button {
+		display: flex;
+		flex-grow: 1;
 	}
 
 	.separator {
diff --git a/src/utils.js b/src/utils.js
index 1747031..d73788b 100644
--- a/src/utils.js
+++ b/src/utils.js
@@ -75,4 +75,6 @@ export const apiFetch = async (path, options = undefined) => {
         state.update(s => ({ ...s, error: 'Received non-JSON response from backend' }))
         return undefined
     }
-}
\ No newline at end of file
+}
+
+export const setStateError = e => state.update(s => ({ ...s, error: e.toString() }))