@media (max-width: 1450px) {
  .main-layout { grid-template-columns: 270px 270px minmax(420px, 1fr); }
  .right-sidebar { display: none; }
}
@media (max-width: 1100px) {
  .top-header { grid-template-columns: 240px 1fr auto; padding: 0 20px; }
  .main-layout { grid-template-columns: 250px minmax(360px, 1fr); }
  .conversation-panel { display: none; }
}
@media (max-width: 820px) {
  .top-header { grid-template-columns: 1fr auto; }
  .global-search { display: none; }
  .main-layout { grid-template-columns: 1fr; padding: 16px; }
  .left-sidebar { display: none; }
  .chat-panel { height: calc(100vh - 115px); min-height: 600px; }
  .chat-header { padding: 0 14px; }
  .chat-actions { gap: 8px; }
  .message-bubble, .image-message { max-width: 78vw; }
}
@media (max-width: 520px) {
  .top-header { height: 70px; padding: 0 14px; }
  .brand { font-size: 22px; }
  .header-actions { gap: 8px; }
  .icon-button { display: none; }
  .profile-menu img { width: 38px; height: 38px; }
  .chat-body { padding: 20px 14px; }
  .message-composer { padding: 0 12px; }
  .composer-actions button:nth-child(1) { display: none; }
}