Riddle of the Sphinx for Atari 2600 is an action-adventure game where players embark on a quest through ancient Egypt. As an archaeologist, you navigate deserts and face mythical creatures like scorpions and thieves to solve the riddle posed by the Sphinx. The game involves collecting treasures, offering items to gods for blessings, and managing resources to survive the perilous journey. With an overhead view, players must decipher clues and avoid dangers to ultimately reach the Sphinx and unlock the ancient secrets it guards.