How to perfect clear

A practical guide to perfect clears (PCs): what they are, why 10 pieces is the magic number, and how to practise them until they feel easy.

What a perfect clear is

A perfect clear is a line clear that leaves the board completely empty, with not a single block left over. Some games call it an All Clear or a Bravo, and players shorten it to PC. In competitive play it's one of the strongest moves there is, and in practice it's a great test of planning, because you have to see the whole shape before you place the first piece.

The 4-line PC uses exactly 10 pieces

Four full rows of a 10-wide board is 40 cells. Every piece covers 4 cells, so a 4-line perfect clear takes exactly 10 pieces, no more and no less. With hold, 11 pieces pass through your hands: you place 10 and the last one stays in hold. So a PC is really about choosing which 10 of the next 11 pieces to use.

A smaller PC is possible too. Two full rows is 20 cells, which is 5 pieces, but it only works with the right pieces at the right time. Without garbage coming in, a perfect clear can only happen after an even number of total cleared lines.

Bag positions: PC #1 to #7

Modern games deal pieces in bags of 7, one of each shape, in random order. Your first PC starts at the top of a bag. It uses 10 pieces, which is one full bag plus 3 from the next, so your second PC starts 3 pieces into a bag, the third starts 6 in, and so on. After seven PCs you are back at the start of a bag. That gives seven different starting positions, which players call PC #1 to PC #7. Each one feels different, because you know a different amount about which pieces are left in the current bag.

The Perfect clear trainer lets you pick any of the seven positions with the PC # selector, so you can drill the ones you find hardest.

Your first PC: the Perfect Clear Opener

The best-known setup for the very first PC is the Perfect Clear Opener, or PCO. The L, J and O pieces stack into a block against one wall, and the T, S and Z pieces form a sloped stack against the other. The I piece waits in hold, and the gap in the middle is filled with the first pieces of the second bag. According to the Hard Drop wiki, PCO succeeds about 84.6% of the time if you keep the I piece in hold through the first bag, and about 61.2% if you have to stand it upright beside the block instead.

You don't need to memorise setups to start. Learning to read the space, below, will get you surprisingly far on its own.

Rules that save attempts

• Never cover a hole. An empty cell under a block means that row can't clear, so the PC is gone.
• Count cells in pockets. Split the empty space into separate pockets in your head. Each pocket has to hold a multiple of 4 cells, or no set of pieces can fill it.
• Keep the stack flat on top. A PC fills 4 rows exactly, so the space left should stay low and simple, without deep wells you can't reach.
• Save the flexible pieces. I and O pieces are the easiest to fit into whatever is left at the end. T, S and Z are the ones that tend to leave awkward shapes, so place them early.
• Learn a few spins. The most common ones in perfect clears are S and Z spins into a flat position, and L and J spins that end with the flat side down.
• Don't give up on a miss. If a 4-line PC falls apart, a 6-line or 8-line PC is sometimes still possible.

How to practise

• Play the daily. Every day stackdle.io has three perfect clear puzzles, the same for everyone, with 3 hints for each. Every puzzle has been checked by the solver, so a solution always exists.
• Use the trainer. In the Perfect clear trainer you get endless PCs with a solver beside you. It tells you whether a PC is still possible with your pieces, and can show the whole solution, step by step.
• Fix your finesse. PCs often come down to speed. The finesse drill teaches you to place every piece with as few key presses as possible.
• Go slowly first. Getting a PC right at a slow pace beats rushing and missing. Speed comes once the shapes feel familiar.