... , game ideas aren't copyrighted , he can make a tetris clone with his own assets and no one will harm him ...
Whiteclaws
From the U.S. Copyright Office: "Copyright does not protect facts, ideas, systems, or methods of operation, although it may protect the way these things are expressed."
So in the case of Breakout this means, you may very well have an idea of a paddle pushing a ball that destroys bricks of a wall and bounces back. But when shaping this idea to a game, it MUST NOT be similar to the game Breakout. By substantially altering it, you avoid copyright infringement. For example, use a slingshot instead of a paddle, use real world physics and let the bricks of a wall instead be balloons floating in the air. Now it's your own original work and no derivative anymore. Unless you describe somewhere, that you based this game on Breakout...
In the case of Tetris I can only recommend what I already said about Breakout. It simply isn't sufficient to just make Tetris with your own assets. I'd again say to google it, but to make your search easier, I'll link to just one of so many articles about it: http://www.webpronews.com/tetris-clones-beware-you-may-be-held-accountable-for-copyright-infringement-2012-06