You should seriously go check out Polygraph. Four versions of a delightful and challenging game:
- Lines
- Parabolas
- Rational functions
- Hexagons
The hexagons will be familiar to long-time readers of this blog.
I have run the parabolas version in College Algebra, and the hexagons version in my Ed Tech course. It was a huge hit both times—lots of conversation happened both electronically and out loud in the classroom. It’s a ton of fun.
I am especially pleased with the rational functions version. It makes for challenging work—even among the mathematically astute Team Desmos in recent trial runs.
Read the Desmos blog post on the matter if you like.
Overthinking my teaching 
Hi Christopher, I was excited to see your article in the most recent Math Teaching in the Middle. I was intrigued about the mention of calculus and about your list of what is part of the Elementary Algebra topics. When I went to the end of the article to read about its author, I smiled when I saw your name. I will be sure to share with the middle school teachers. Just today, a high school teacher was talking about CCSS at the high school level and that the only way they were going to be able to meet the high school standards of the CCSS was to push some stuff to the middle school. This didn’t make me happy. We are using CMP3 and I feel like our plates are full. I mentioned to the high school teacher that perhaps after they’ve aligned with the CCSS they might be able to let go of some content that they’ve been teaching. hmmm Thank you for your sharing.
Jenny Jorgensen Math Lead Teacher F. H. Harrison Middle School Yarmouth, ME 04096