## File: `assets/css/chat.css`
```css
#group-chat-container { max-width:600px; margin:0 auto; display:flex; flex-direction:column; height:80vh; border:1px solid #ccc; }
#chat-messages { flex:1; overflow-y:auto; padding:1rem; }
.chat-bubble { display:inline-block; padding:.5rem 1rem; border-radius:1rem; margin:.5rem 0; max-width:80%; }
.chat-bubble.user { background:#dcf8c6; align-self:flex-end; }
.chat-bubble.other { background:#fff; align-self:flex-start; }
#chat-form { display:flex; flex-wrap:wrap; padding:1rem; gap:.5rem; }
#chat-form select, #chat-form textarea { flex:1 1 100%; }
#chat-form button { flex:0 0 auto; }