Screenshot of graphing game

This is for my graphing game I'm working on. Right now the object of the game is to write an equation that will make a graph to intersect with the green dots but not with the grey dots. It is like a game that I used to play a long time ago. A while ago I wanted to play it, so I searched on the web and found it was $60 and it looked like it hadn't been updated in 10 years. So I just decided to write my own version.