diff --git a/index.html b/index.html
index c5470c1..90b382b 100644
--- a/index.html
+++ b/index.html
@@ -17,7 +17,7 @@
                         <option value="" selected>Select a state…</option>
                         <option v-for="state in states">{{ state }}</option>
                     </select>
-                    <button class="btn btn-primary" type="button" @click="launch" :disabled="launched">Play</button>
+                    <button class="btn btn-primary" type="button" @click="launch" :disabled="launched || !state_name">Play</button>
                 </div>
                 <div class="btn-group">
                     <button class="btn btn-secondary" type="button" @click="save" :disabled="!launched">Save</button>