1. Oil futures did not go to zero, dummies. Learn how futures contracts work.
2. Been a while since we've seen $25+ oil, which is why we see the light blue, orange, and purple levels above price.
3. That said, I can't recommend shorting the bottom on oil. Oil from $20 - 23 is a 10% increase, and we're pretty clear to get back to $23-24. You could easily blow out your account if oil prices suddenly rise 10% one day ($20 to $22).