body {
  font-family: system-ui, Arial;
  background: #f7f7fb;
  color: #111;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  padding: 20px;
  margin: 0;
}

#app {
  width: 100%;
  max-width: 720px;
  background: white;
  border-radius: 12px;
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.1);
  padding: 20px;
  display: flex;
  flex-direction: column;
  height: 80vh; /* take more vertical space */
}

#messages {
  flex: 1; /* grow to fill available space */
  overflow-y: auto;
  border: 1px solid #eee;
  padding: 12px;
  margin-bottom: 12px;
  background: #fafafa;
  border-radius: 8px;
}

.msg {
  margin: 6px 0;
  line-height: 1.4;
}

.msg.system {
  color: #666;
  font-style: italic;
}

.msg.user b {
  color: #4caf50;
}

.msg .ts {
  color: #999;
  font-size: 0.75em;
  margin-left: 6px;
}

#msgForm {
  display: flex;
  gap: 8px;
}

#msgInput {
  flex: 1;
  padding: 10px;
  border: 1px solid #ddd;
  border-radius: 8px;
}

#msgForm button, #leaveBtn, #joinBtn {
  padding: 10px 16px;
  border: none;
  border-radius: 8px;
  background: #4caf50;
  color: white;
  cursor: pointer;
  font-weight: bold;
}

#header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 12px;
}