Replacing Galactic Civilizations III on Epic Games Store's giveaway list is Mighty Polygon's 2020 title - Relicta.
"Relicta is a first-person physics-based puzzle game where you need to creatively combine magnetism and gravity to unravel the secrets of Chandra Base. Alone in the depths of the Moon, your scientific mind is the only thing that can keep your daughter alive…" the game description reads.
Playing as a top physicist, players will have to rush ahead, solve puzzles, and get to safety. Or, they can take their time to gather clues and discover the intrigues of 22nd-century orbital politics. To solve the physics-based puzzles, players only need to manipulate gravity and magnetism.
Relicta can be claimed for free here.