Cave Story's Secret Santa [PC]
until January 7th 11:59PM Pacific
Store descriptions say this is available for a limited time despite the regular free label, and GOG's announcement post includes a specific end time.
Steam: https://store.steampowered.com/app/1812280 (no +1 game count)
GOG: https://gog.com/game/cave_storys_secret_santa
Epic Games: https://epicgames.com/p/cave-storys-secret-santa-b6d437
