Tetrollapse Light

How does the game Tetrollapse Light work?

New version of the classic puzzle game, Tetris. The rules of the game are simple and well-known. You'll have to turn the pieces and horizontal lines so they disappear. The objective is to survive for as long as you can without letting the pieces fill up the screen. However, a condition has been added: at the beginning of each level, there'll already be pieces on the board.