Never Bury a Hole

A covered gap costs you every row above it. Taking a worse placement to avoid one is nearly always correct.

A hole is an empty cell with at least one filled cell above it. It is the most expensive object in the game.

Why they are so costly

A hole makes every row above it uncompletable. Not harder: impossible. Those rows cannot clear until you remove everything on top of the hole and fill it.

So a hole buried under four rows has effectively deleted four rows of your playing field. Your usable well just got shorter, and it stays shorter until you spend several pieces digging.

Two holes in different columns, at different depths, is often a run that is already over and has not noticed yet.

The trade you should almost always take

The situation arrives constantly: the clean placement raises a column by three, and the neat-looking placement buries a hole.

Take the ugly one. A tall column is temporary. Pieces will arrive that fit beside it, and the surface will level out. A hole is permanent until you excavate it, and excavation costs pieces you would rather spend clearing.

Height is a debt with a low interest rate. A hole is a debt that compounds.

Where they come from

Almost always S and Z pieces placed on a flat surface. Both shapes are two offset pairs, so laying one flat guarantees a gap beneath one end.

The others are hard drops fired before you finished rotating, and I pieces laid flat across an uneven surface.

The habit to build

Before committing, look at the cells under the piece, not just the ones it occupies. The ghost outline tells you where it lands; what matters is whether anything is left uncovered beneath it.

When you already have one

Dig it out early. A hole under two rows takes a couple of pieces. The same hole under eight rows may be unrecoverable. The instinct to build over a problem and deal with it later is exactly backwards here.

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