That's known as positive and negative edge in the fighting game community. Some fighting games (e.g. Street Fighter) actually check inputs at both the positive

That's known as positive and negative edge in the fighting game community. Some fighting games (e.g. Street Fighter) actually check inputs at both the positive and negative edges of button presses, so you can actually hold punch while doing the quarter circle forward and let go as you hit forward. A lot of advanced combos and tricks use negative edge.