Understanding how positive and negative numbers interact

This is part of my submission for Khan Academy's talent search. It is a way for students to visualize combining positive and negative numbers (Without a number line, for now)

This video is based around the fact that opposite quantities combine to make zero (CCSS 7.NS.1a) and is intended for younger students.

It would be a good lesson to give students red and green blocks, and have them represent different exercises using them. After that, have the students pair the blocks up (to make zero each time that happens), and then count how many blocks are left. The color of the block tells the student what sign to use.

I am planning on creating a video where these blocks organize themselves into a number line.