Caixas 1
Inspired by the work of ASCÂNIO MMM. (Cf. http://mathhombre.tumblr.com/post/116580874829/caixa-dois-definitely-in-danger-of-being-obsessed)
This is rough & a bit wonky, but wound up being fun to make and play with.
More GeoGebra at bit.ly/mh-ggb