means, rather than from defeating units. Currency can be used to buy new items and weapons at merchants at specific locations within maps. Items can also be exchanged between units during battles. Battles in the story take place on maps divided into a square-based grid. Battle actions are governed by a turn-based system where each unit on both sides is given their chance to move and act. During gameplay, weather and terrain effects appear such as fog of war or elements of the environment that can be manipulated to one side's advantage, affecting the progress of battle. Units are split between player, enemy and allied non-player character (NPC) units. Each unit's movement range and attack range is displayed when selected. The player must clear a map to advance the story: the objectives for clearing a level can vary from defeating all enemies to capturing strongholds or rescuing NPCs. When engaging a unit, the scene transitions into a battle between the player and enemy unit, with battle animation playing out. When hit with an attack, a character loses health points (HP). For player characters, HP can be restored with items or by units with healing magic; it can also be regained by standing on forts, gates or castles, or using a special spell that replenishes health based on damage dealt to an enemy. Each unit is governed by a character class system, with their class affecting what weapons they can use. After each action in battle gains experience points (EXP). Upon reaching 100 EXP, a unit levels up and its statistics such as attack power and defense are randomly raised, while weapon ranks increase naturally when using their respective weapons. Upon reaching Level 10, and using a special item, a unit's class can be upgraded to a more powerful version with access to new items and weapons. If a unit is defeated in battle, they are subject to permanent death, being removed from all future encounters and the overall storyline with a few exceptions for story-related characters. If characters crucial to the storyline like Lyn, Eliwood or Hector fall, the game ends and the player must restart the level. Weapon strengths and weaknesses are governed by the series' Weapons Triangle system; axes are strong against lances, lances strong against swords, and swords strong against axes. Bows are independent of the system, being effective against airborne units. A similar system, dubbed the