The game is the logical extension of Tetris into the third dimension. In regular Tetris, the player manipulates a set of tetrominoes which fall into a two-dimensional pit (seen from the side). The aim is to solve a real-time packing problem by forming complete rows, which then disappear and score points. Poor play leads to incomplete rows, caused by inefficient arrangements of tiles; these rows do not disappear, giving the player progressively less space and less time to play subsequent pieces. Similarly, in Blockout, the player manipulates a set of polycubes which fall into a three-dimensional pit (seen from above; the pieces appear in the foreground and fall away). The pieces can be rotated around all three axes, and moved horizontally and vertically. The aim is to form complete layers.
The New York Times reviewed the game in an article about educational software for mathematics, writing that Blockout "doesn't pretend to be educational, but the skills required to master it are not unrelated to mathematics, particularly geometry." A 1993 study found evidence that playing Blockout improved the spatial visualization ability of 10- to 14-year-olds.Dragon gave the game's Atari Lynx version a perfect score.