It like riddles, praps it does, does it? Then it is in luck! The riddle/adventure game Under The Moon is free to claim on GOG for the next three days.
(claim from the banner on their front page)
– Account required: GOG.com with e-mail marketing opt-in
– DRM-Free (NOT Steam)
– Offer ends May 01, 1300 GMT.
– Steam Store for comparison
Enjoy the game.