Nostalgia is a traditional console role-playing game featuring three-dimensional characters and environments. Players control a young London boy named Eddie and his compatriots as they travel across an alternate history 19th-century Earth on a high-powered zeppelin, visiting various locales and raiding ruins in order to uncover the truth about an ancient civilization, as well as find Eddie's lost father. In order to advance the story, players must visit towns and interact with non-player characters to obtains clues on their next destination, as well as traverse dangerous dungeons and environments in order to find hidden treasures. Taking advantage of the Nintendo DS's dual screens, gameplay is featured on one screen while a map of the player's current location is present on the other, which fills as they travel through new areas. While traveling through the game, the player will randomly encounter enemies as they move through dangerous areas, which must be defeated in battle.
Battles in Nostalgia use a turn-based combat system where both characters and enemies acting in an order relative to their "speed" statistic. A Combat Order bar is present in battles that shows which of the player's party members or enemies will act next, with the player selecting a character's command just before their turn. In any given turn, a player may choose to attack an enemy, defend, use an item for beneficial effects, or use special skills unique to each character. In addition to ground battles, a player may also encounter enemies while in their airship, leading to a ship-to-ship combat sequence with unique commands. Players must defeat all of their enemies by attacking them until their hit points are extinguished, which grants each character experience points that go towards gaining levels, thus making them stronger and giving them access to more abilities. The player's party is judged at the end of each battle with a letter grade based on their actions in combat, and is determined by how quickly and flawlessly they have defeated their enemies and may give additional rewards.
Source: Wikipedia, "Nostalgia (video game)", available under the CC-BY-SA License.