cleaned up the code to avoid NPE.
Corrected the starting position for tetrominos. Added output lines.
Added an output line. Correction: switched row and column.
Staticly type Game game. Changed the output
Renamed a method to clarify its action
Renamed a method and changed a return value　to reflect the change. Added a movement method.
Fixed incompatible types
Added a new method that places or lifts currentPiece from the well
Call the getter method instead of direct access. Simplified a code block.
Added method calls to a newly created method.
Added API for translations
Added API for rotations