Press the arrow keys when the arrows are over the guide. Alternate keys dfjk are also usable. You gain 100 points for each perfectly timed correct arrow. Doubles only count if you hit both together, but both arrows give you points. You lose 20 points for hitting a key when an arrow is not lined up. You gain a 5% bonus for each arrow you hit without missing one or screwing up. You have a 0.2 second margin for error before and after each block's track section, but get reduced points for a late or early hit.