更新：左下角一起浮现，更方便
.excalidraw .Island.App-toolbar,
.excalidraw .mobile-misc-tools-container,
.excalidraw .App-bottom-bar
{
opacity: 0;
transition: opacity 0.3s ease-out .2s;
}
.excalidraw .Island.App-toolbar:hover,
.excalidraw .mobile-misc-tools-container:hover,
.excalidraw .App-bottom-bar:hover
{
opacity: 1;
}