Alternating sum of squares animation

Animation showing that the alternating sum of squares is a triangular number.

<video controls autoplay loop> <source src="https://s3-us-west-1.amazonaws.com/hmt-forum/perfect_square_animated.mp4" type="video/mp4"> Your browser does not support the video tag. </video>

Previously:

https://www.homemadetools.net/forum/...420#post135480
https://www.homemadetools.net/forum/...015#post179894
https://www.homemadetools.net/forum/...422#post127363
https://www.homemadetools.net/forum/...348#post165895
https://www.homemadetools.net/forum/...030#post153256

Alternating sum of squares animation - GIF