Shining Force EXA is the successor to Shining Force NEO and inherited that game's battle and action RPG mechanics.
One new feature of EXA is the customizable robot castle Geo-Fortress. While adventuring, the party members left behind use the Geo-Fortress as a headquarters. They also protect and defend the castle in the event of an attack. In the beginning, the fortress is very basic and vulnerable. By collecting "Rare Material" from the given quests, the player is able to transform the fortress into two other forms. Once the fortress reaches the third form, it is capable of travel. The player is able to add more rooms for vendors and shops. In addition to a traveling store, the player is also able to train party members. The growth, layout, and defense of the fortress is managed completely by the player, thus allowing the Geo-Fortress to evolve to fit the style and tactics of the player.
The player upgrades characters through experience points and an assortment of items and weapons. In addition, using specific battle tactics of the party will grant it more power and range. As well as advancing the main character, the player progresses to master a variety of Power Arts to unleash special and magic attacks.
Source: Wikipedia, "Shining Force EXA", available under the CC-BY-SA License.