Starting at the beginning of battle, both you and your opponent have 0 points in their Mega Bar. Each turn, you and your opponent gain 1 point each, capping at 5. When you reach 5 points, you can have the pokemon with their respective -nite megavolve. However, having the pokemon with the -nite in battle would increase the bar by 2 points every turn for the pokemon's side. If the mega form switches out, the counter for the pokemon's side is reset to 0, and the pokemon reverts to its original form. In-game items can give you a full meter, and will use as many Wonder Launcher points as Full Restores.