Contents > Introduction

Infinite Playfield

On an infinite playfield, tetrominoes spawn at “row infinity” and column zero. When a newly spawned piece falls, it never gets closer to the floor due to the nature of infinity. This means, in finite—though potentially vast—time, the agent can shift the piece into any finite column. And once in position, the agent can hard drop the piece.

A hard drop attempts to vertically translate the piece from “row infinity” to row zero, crossing all the space in between in the same time it takes to perform a soft drop. Along the way, the piece can encounter a barrier of solid cells that stops it. And, once stopped, the piece locks into place.

A more generalized version, the semihard drop, attempts to vertically translate the piece from “row infinity” to a specified, finite row. If it encounters a barrier along the way, it locks into place. Otherwise, the agent is free to shift, rotate, and drop the piece from there. A semihard dropped piece does get closer to the floor as it falls because the move puts it on a finite row.

The agent is limited to actions that take finite time. For instance, it cannot clear a line because it cannot carry out the infinite moves required to arrange infinite pieces into a line. Consequentially, the game never advances to the second level. It permanently runs at the lowest drop speed.