Playfield: a rectangular grid, commonly bounded by walls.; The snake: starts as a short segment and grows by one per item eaten.; Food: a single item appears at a random free cell; eating it spawns another.
Why people argue about this
People often assume that the snake can grow in any direction they choose after eating food, when technically it must extend only vertically or horizontally along its current body length. The confusion arises because the official description doesn't specify how exactly the snake's segments move post-eating.