Quartet is a platformer game where Mary and Edger jetpack their way through six rounds, searching for Queen Cynthia's casket. The duo must navigate through enemy-riddled levels with limited vitality, represented by a countdown timer. Defeating each boss earns them a key to unlock the next round. Players receive bonus points and medals based on their performance in each round, with higher ranks awarded to those who complete rounds quickly.
The gameplay involves Mary and Edger jetpacking through levels, avoiding obstacles and enemies while trying to reach the end of each stage. The game features six challenging rounds, each with its own unique challenges and enemies. Players must work efficiently to complete each round within a limited time frame, as their vitality decreases with each passing second. With each boss defeated, players unlock access to the next round, where they can earn rewards and improve their ranking.