

Yeah, but that’s only really a trap is there’s a way to keep him from escaping. Voldemort escaped pretty easily; had Harry not been there, he could’ve tried for some time, figured out the trick and then just left to re-evaluate his options.
While not explicitly stated, it’s possible that that’s actually what he did: If he’d figured out Harry, Ron and Hermione had been snooping around and had found the room with Fluffy, Quirrel might’ve willingly dropped hints so that they’d check, let the music play longer than he needed to so that they’d know someone was trying to take the stone and he could lure them all the way down.
“Bad” I can’t say, you took no risk, and thus made no mistakes, but also displayed little skills.
Using triangles for the bodies is a good idea, as triangles are a good shape, you can do anything with triangles. Have you consider increasing the amount of triangle, as such?
I dropped the round heads in the last one, because honestly, circles are an overrated shape. And you can do anything in triangles, why use anything else?
You can find any number of foolish ressources online, none of them tells you the truth about triangles. All sorts of websites and yet more websites try to teach you how to draw, without even mentioning triangles in any of their tutorials.