For those interested, this article defines many field metrics such as number of holes, surface smoothness, and blocks above holes. Colin Fahey goes into it a little on his site, too. Tetris playing algorithms weigh these different metrics to decide what's the best place to drop each piece.
But the algo doesn't try for large line clears, it just tries for any line clears, and for playing as long as possible. It also measures progress by number of lines...
oh i didn't realize that was what herc was trying to get at. they still describe a bad playing field.
