Easy — shape sampling: all 15 base shapes are equally likely, so simple pieces (singles,
dominoes) come up often.
Hard — uniform sampling: all 43 distinct oriented pieces are equally likely, so complex pieces
with many rotations (pentominoes, J/L) dominate and tiny pieces get rare.
Each mode keeps its own high score. Switching modes starts a new game.
iPhone / iPad: tap the Share icon, then Add to Home Screen.
Android: open the browser menu (⋮), then Install app / Add to Home screen.