TYPOTRIS
THE GAPS THE PIECES LEAVE BEHIND SPELL THE MESSAGE
Exact letters. Completing a row makes it vanish and leaves the blocks above it hanging, which is the only way a falling piece ever ends up over a gap. Every character is precomputed, so it draws instantly.
SLOWFAST
10 COLUMNS PER BOARD · THE LEFT COLUMN IS LEFT OPEN SO NO ROW EVER COMPLETES BY ITSELF