Comment by schoen

Unless there's a different kind of rotation in later levels, what happens after forming a line is equivalent to having the existing structure "collapse" under gravity (any suspended blocks fall straight down). This is purely beneficial to the player, and means there's a bit less strategy involved than I would first have thought: you can just play normally and any errors will get fixed every time you complete a line!

Edit: I'm kind of wrong about that because there's a different kind of rotation that happens if you form a complete vertical line.