next.js/packages/next/src/next-devtools/dev-overlay/components/toast/style.css

.nextjs-toast {
  position: fixed;
  z-index: var(--top-z-index);
  max-width: 420px;
  box-shadow: 0px 16px 32px rgba(0, 0, 0, 0.25);
}

.nextjs-toast-errors-parent {
  padding: 16px;
  border-radius: var(--rounded-4xl);
  font-weight: 500;
  color: var(--color-ansi-bright-white);
  background-color: var(--color-ansi-red);
}