A perfect clear, also called all clear or bravo, is performed when a player locks a line clearing piece resulting in a completely empty playfield.
In some games, a perfect clear awards the player with a score bonus, or in multiplayer sends garbage lines.
While perfect clears are quite rare in most older Tetris games, the usage of the Random Generator in modern Guideline games allow the player to perform perfect clears with relative ease and a high success rate by creating two shapes with the first bag: a 4x4 square and a TSZ stack. The rest of the playfield can be filled in various ways.
The shape of the initial stack can also vary according to the placement of each piece. Here, a 6x4 rectangle shape is formed on the left side while a T piece sits next to the stack or is on the other side of the playfield.
Other setups, such as the examples below, can also result in 4-line (Tetris) or 6-line perfect clears.