You could have downloaded Briblo 1.0 for Mac from our application library for free. The program lies within Theming Tools, more precisely Screensavers.
From the developer:
Briblo is a stacking brick style screen saver game.
The twist is that it is in oblique view, so you have two axes' in which to rotate & move you pieces as they fall.
The cursor keys move your piece, and the space bar rotates it.
Works with dual screens!