Ilamentia | IndieGameStand | Beat the minimum ($1/£0.59)
Plenty of games have tried to muscle in on the first-person puzzling territory after that Valve game, but Ilamentia stands out by way of being so effortlessly surreal. Its puzzles range from spatial navigation to audio challenges and jump scares, tied together with a gorgeous aesthetic.
If that sounds like your cup of tea, you can buy the DRM-free version for 59p at IndieGameStand. You'll also receive Desura/GOG/Steam codes if and when it releases on those platforms.