First: Great job and I’m proud of you for giving this a stab 🙂 As the teacher I appreciate the effort you put in!
So.. with that said, check out this solution: https://jsbin.com/cuqiba/8/edit?js,output
Third: To make sure you really get it, try figuring out this similar example on your own: https://jsbin.com/wayapuf/edit?html,js,output
Let me know how it goes! This should help begin to solidify the benefit of querySelector.