Code the game Tetris on Dr Racket

The game should include the essentials, like pieces dropping into place, rotating the pieces, clearing a row, rows advancing, and scorekeeping. 

The file should have structures, unit tests, and purpose statments for each function. Also, the world should be represented by rows and columns, the world structure should include (piece, heap, and score)

the game should inclode some of these abstract functions: (foldr, filter, map) as well as lists.