Considered by many to be one of the defining indie games, this 2004 metroidvania adventure “received widespread critical acclaim for many polished aspects of its design, such as its compelling characters, setting, story, and gameplay”. While the enhanced Cave Story+ has been given away before, the original is available on Windows, Mac, Linux, Android, half the consoles released in the last few decades (including GameCube, PSP, and Megadrive), Amiga, and even some Motorola devices!
I’ve only played the original Freeware title. I can definitely recommend this. At the time I played it, it had an incredible impact on me, opening the door to the world of indies and the freeware scene in general. I can credit it with having a direct influence on me trying game development as a hobby. It’s wild how amazing of a game and how much polish it has for a free game made in 2004 by one dude. 20 years ago!
… Also, I’ve been reading forum threads debating if this is a metroidvania since at least 2010, possibly even earlier!