The "15 Puzzle," also known as the Gem Puzzle or Mystic Square, is a popular sliding puzzle game that challenges players to arrange numbered tiles in the correct order. The puzzle consists of a set of square tiles placed inside a rectangular grid, with one empty space that allows for tile movement. The objective is to reorder the tiles into ascending numerical sequence by strategically sliding them around the grid. The puzzle offers various versions, including those with images instead of numbers, adding a creative twist to the classic challenge. The goal is to complete the puzzle in as few moves as possible, testing both logic and problem-solving skills.