Thanks for playing!
The game has a lives system that is on by default, but you can turn it off in the settings if you prefer. What the lives system does is that every time you hit an obstacle it sends you back to the last safe spot you threw the boomerang from so long as you have lives left. You can see how many lives you have when you hit an obstacle - they show up above the boomerang, and the one you just lost blinks out. Essentially, you can hit obstacles 4 times before being sent back.
Obstacles are generally black and cast a long shadow, as if going all the way up to the ceiling. We've noticed shadows might not display if the graphic settings on the launcher are set to lower than Medium, so I recommend setting them to anything above that, or straight up Ultra - the game shouldn't require too much to run at these settings, but let me know if that's not the case.
I don't understand what you mean by "kind of hovers at random points", could you elaborate?