Question about $SSPC: how does it work?

As many of you know, it's something like a "2x Short SPCX Daily ETF" . I was looking at it, and noticed that if $SPCX was down x%, $SSPC was up 2\*x%, almost exactly. How are they able to achieve this? I'm just wondering what the mechanics of this fund are.

And if one were bearish on $SPCX and buy $SSPC, is it safe to hold it for a period of time (months)? Or should one get in/out every day, since the name says "Daily".