Upon using the attack, Luigi eats a Mega Mushroom and becomes Mega Luigi, similar to the Giant Battles in Mario & Luigi: Dream Team. At this point, Luigi will start charging towards the enemy with his hammer (which Mario jumps on beforehand), and the player must press every time one of his feet touches the ground to make him faster. Upon reaching the enemy, must be pressed to hammer the enemy away (which also damages any other enemies on the battlefield nearby). Mario will then fall towards the flying enemy, and the button must be pressed each time he is about to land to bounce off the enemy and keep the chain going.
If the player does not press when Luigi approaches, then he falls over and the attack will fail with only minor damage done to the enemy. Once the enemy has been hammered into the air, then each well timed press of will increase the attack rating, going from OK (if Mario only stomps the enemy once) to Excellent (if he manages to stomp it four times in a row). An Excellent rating will also cause Mario and the enemy to slide across the ground for a bit afterwards, doing even more damage.
Unlike other attacks in the game, Mega Thwonk does both hammer and jump damage to its target. Hence, an enemy immune to hammer attacks (like Bowser Jr.) will only take damage from Mario's jumps afterwards, and a spiky enemy (like Spinies) will only take damage from the initial hammer strike (Mario will bounce off the enemy in pain upon trying to land on it).
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