Lines now stay on the screen for a second before disappearing.
Refactoring: moved some reusable code to GameState.
Added animation!
Refactoring: use a common constant.
Javadoc improvements.
Code style.
Refactoring.
Reduced the amount of time lines stay on the screen.
Refactoring: moved animation logic to BlockStyle.
Code style: extracted some methods.
Slightly brighten disappearing lines.