>>12675024It's a momentum meter. You always start with it neutral (green). Successfully attack and taunt and it goes up, get attacked and get taunted on and it goes down. To simplify it, the higher your momentum and the lower your opponent's, the more likely you will be able to pull off big moves like powerbombs and DDTs without getting reversed. When you're both at neutral, you'll have to stick to light grapples like arm wrenches to avoid getting repeatedly countered. If your opponent has high momentum, even light grapples will get countered a lot and you're going to have a difficult time coming back. It's the defining mechanic of the series, and your matches can vary from incredibly quick squashes to lengthy slogs depending on how well you can land the first big attacks and gain control at the start.
