```css
.float-btn {
  position: fixed !important;
  bottom: 20px;
  right: 20px;
  z-index: 999;
  max-width: 300px;
}

@media (max-width: 960px) {
  .float-btn {
    bottom: 10px;
    left: 10px;
    right: 10px;
    max-width: none;
    width: calc(100% - 20px);
  }
}
```