Undertale is a role-playing game that uses a top-down perspective.In the game, players control a child and complete objectives in order to progress through the story. Players explore an underground world filled with towns and caves, and are required to solve numerous puzzles on their journey. The underground world is the home of monsters, many of whom challenge the player in combat;players decide whether to kill, flee, or befriend them.Choices made by the player radically affect the plot and general progression of the game, with the player's morality acting as the cornerstone for the game's development. When players encounter enemies in either scripted events or random encounters, they enter a battle mode. During battles, players control a small heart which represents their soul, and must avoid attacks unleashed by the opposing monster similar to a bullet hell shooter.As the game progresses, new elements are introduced, such as colored obstacles, and boss battles which change the way players control the heart.Players may choose to attack the enemy, which involves timed button presses.