Horror House by Booming Games offers a chilling slot experience set in a haunted mansion, starting with a 5x3 grid and expanding to 5x5. Each winning combination opens up more positions on the reels, and consecutive wins trigger respins with increasing reel sizes, leading to 3125 ways to win. Landing three or more Scatter symbols awards the Free Spins feature, where the grid remains fully expanded for increased winning potential and spooky thrills.