#sound-toggle {
  position: fixed;
  right: max(20px, env(safe-area-inset-right));
  bottom: max(20px, env(safe-area-inset-bottom));
  z-index: 10;
  min-height: 44px;
  padding: 10px 16px;
  border: 1px solid rgba(255, 255, 255, 0.45);
  border-radius: 2px;
  color: #fff;
  background: rgba(9, 13, 21, 0.8);
  font: 12px/1.4 system-ui, sans-serif;
  letter-spacing: 0.08em;
  cursor: pointer;
}

#sound-toggle:hover { background: rgba(35, 42, 55, 0.95); }
#sound-toggle:focus-visible { outline: 2px solid #fff; outline-offset: 4px; }
#sound-toggle:disabled { opacity: 0.55; cursor: wait; }