The Wings of Liberty campaign contains several missions with unique features, such as lava that floods the battlefield every five minutes, forcing the player to move their units to high ground before they're destroyed. In another mission, enemy units will only attack the player at night, forcing the player into a form of siege warfare. Finally, in one mission, the player must use a single unit to influence the tide of an AI-controlled battle. The single player missions are highly customizable and are featured in the StarCraft II Community Zone. Between missions, players can choose units, buildings, and upgrades that are not available in the multiplayer missions. A major new addition to the map-making community will be the StarCraft II Marketplace, where high quality maps will be sold for a small fee as "premium maps" over Battle.net. The mode of payment has not yet been announced. Lead Designer Dustin Browder has mentioned that even maps like player-created Defense of the Ancients in Warcraft III would not meet the quality requirements to be branded as a premium map.