Linear Inequality Game

Inspired by Dan Meyer's post: http://blog.mrmeyer.com/2015/if-graphing-linear-inequalities-are-aspirin-then-how-do-you-create-the-headache/ In this game you're trying to guess a linear inequality by guessing points. When you find a true point, you can guess the inequality. The applet always picks a line through two visible points with integer coordinates. So it is very helpful to be able to find an equation of a line through two points. Most of my guesses look like y <= (slope)(x- xcoordinate) + ycoordinate. Very interested in feedback, so please comment, email or tweet me!
More GGB at bit.ly/mh-ggb