Does it? It doesn't seem to affect mine at all. Edit: when the tab is focused it looks like it uses just under 4% of CPU in Firefox, and none when it's not focused. I don't know if that means 4% of total machine CPU or 4% of CPU that Firefox is using.
On my Macbook Pro running Mohave, Firefox uses 14% CPU for about 50 tabs. When this snow globe thing is running, it uses 36% according to top. These are minimums; it periodically spikes higher.
