TETRIS GLOSSARY
Perfect Clear Opener
Also called PCO · PC opener
A starting construction aimed at a four-line Perfect Clear. Its finishing pieces depend on the second bag and hold. If the finish is unavailable, switch to a continuation instead of forcing an impossible empty board.
View in the A–Z glossary →Perfect Clear. Colored cells show the first-stage reference, not placement order. Later bags, clears and alternative routes are not shown.