OPENERS · LESSON 4 OF 6
Perfect Clear Opener
AFTER THIS GUIDEYou can distinguish building the PCO base from solving its remaining spaces, and avoid treating the base as a guaranteed Perfect Clear.
The base is a question, not the answer.
Perfect Clear Opener builds a familiar low shape and then tries to empty the board using the incoming pieces. A four-row empty-board clear accounts for forty cells, or ten tetrominoes. The opening bag supplies seven, so the continuation necessarily involves pieces beyond it.
The space left by a base can have several solutions. A solution tree branches on available pieces, their order and whether Hold can rearrange them. A final tiling picture is insufficient if an early placement blocks the entrance required by a later one.
I in Hold can increase your options in familiar PCO continuations, but a probability quoted for a reference pattern assumes particular rules and solution knowledge. It is not a guarantee for the route you happen to remember.
When no reachable solution fits the visible pieces, keep the board playable. Lowering the stack or opening a well is a valid outcome. Resetting every unsuccessful PC teaches less than understanding how to leave the attempt.
Count, fit, then test the order
Read the target base
The first-stage diagram shows the trainer’s reference arrangement. Locate the open region separately from the coloured pieces. Identify which pieces would become trapped if the roof were completed early.
Account for the spaces
After the base is built, count the remaining cells in the intended clearing rectangle. Divide by four to determine how many pieces you need, then compare with the available queue and Hold.
Check the whole ending
Before dropping the final candidates, trace their entrances. At completion, inspect the entire board: a four-line clear with one cell above it is not a Perfect Clear.
Perfect Clear. Colored cells show the first-stage reference, not placement order. Later bags, clears and alternative routes are not shown.
One O-shaped space remains.
Both remaining rows are full.
Zero blocks left. Perfect Clear.
Play through one verified bag sequence
This is one supported reference route under the TETR.IO profile, not a prescription for every bag. Advance one locked piece at a time; each picture shows the board after any line clear. The practice mode may generate a different compatible sequence.
Start on an empty board. First bag: Z → I → J → O → L → T → S. Hold starts empty.
1. Place Z. No line clear.
2. Place I. No line clear.
3. Place J. No line clear.
4. Place O. No line clear.
5. Place L. No line clear.
6. Place T. No line clear.
7. Place S. No line clear.
8. Place J. 1 row cleared; the picture shows the result.
9. Place T. 2 rows cleared; the picture shows the result.
10. Place I. 1 row cleared; the picture shows the result.
Common mistakes
Stopping at a correct-looking base
The continuation is the actual PC problem. Read it before spending the flexible piece you need later.
Equating area with a solution
A multiple of four is necessary for an isolated cavity, but shape and reachability can still make it impossible.
Forcing a PC after the queue invalidates the route
Change plans while the surface still has a useful escape. Ordinary line clears are allowed to be the sensible choice.
TAKE IT TO THE BOARD
Solve the ending, or explain the exit
- Open Openers and select Perfect Clear Opener. Use Gravity Off and NEXT 5.
- Complete the base, then count its remaining spaces. Name the next required piece before following a suggestion.
- Run three attempts. For each, explain either why the finishing order works or which dependency would make another order fail.
What counts as progress? You understand both the base and the queue-dependent completion, without assuming a familiar shape guarantees a PC.
Open practice ↗Opens the mode. Set Gravity and NEXT yourself; your current settings are kept.
Keep these terms nearby
NEXT IN THIS PATH
MS2 and Gamushiro
Explore two openings with Perfect Clear continuations.
Read the next guide →Further reading
For setup variations and additional examples, see FOUR: Perfect Clear Opener. The practice task here is original to Stacking Lab.