Reserve Stack
Clear four five-cell rows using exactly four tetrominoes: T, I, L and O. The one-piece reserve starts empty. Hold stores the current piece or swaps it with the reserve, once per drop; after the queue runs out the reserved piece becomes the final piece. Rotate turns the current shape clockwise, and tapping a column drops its leftmost edge there. Pieces fall rigidly and full rows clear. Nothing new spawns after these four pieces, so reserve timing and cavity shape matter more than speed. Overflow or exhausting the pieces before four rows ends the run.
About this experiment
Clear four five-cell rows using exactly four tetrominoes: T, I, L and O. The one-piece reserve starts empty. Hold stores the current piece or swaps it with the reserve, once per drop; after the queue runs out the reserved piece becomes the final piece. Rotate turns the current shape clockwise, and tapping a column drops its leftmost edge there. Pieces fall rigidly and full rows clear. Nothing new spawns after these four pieces, so reserve timing and cavity shape matter more than speed. Overflow or exhausting the pieces before four rows ends the run. Keyboard: Tab and Enter/Space operate buttons; R restarts.