Vim-Vixen/src/command-line/command-line-frame.scss

.vimvixen-command-line-frame {
  margin: 0;
  padding: 0;
  bottom: 0;
  left: 0;
  width: 100%;
  height: 20px;
  position: fixed;
  z-index: 10000;
  border: none;
}