The Tetris Font is a typeface where each letter and digit is made up of exactly one of each of the seven Tetris pieces. The font was designed by Erik Demaine and Martin Demaine, with the help of the BurrTools software. The letters are designed to be constructible by stacking the Tetris pieces one at a time, following the standard Tetris rules. The font also features puzzles and animations, allowing users to guess the letters before they are fully constructed.