The standard endless mode in the NES version of Tetris is called A-Type. In this mode, players keep clearing lines and aim for the highest possible score until the stack reaches the top.
A-Type differs from B-Type, the NES version’s fixed-objective alternative. B-Type begins with randomly arranged blocks near the bottom of the well and ends after the player clears 25 lines. A-Type has no fixed line-clear target; its challenge comes from increasing speed and the player’s ability to survive.
In A-Type, the level normally advances after every 10 cleared lines, increasing the falling speed and changing the scoring environment. Players can choose a starting level, allowing them to begin with faster pieces. The game’s celebrated rocket-launch endings also occur after an A-Type run, with the animation depending on the score.
Modern Tetris games often call comparable play Marathon mode, which causes confusion. Sprint is a timed challenge, while Marathon is a later naming convention; on NES, the canonical label is A-Type.