Possibly the most underrated game ever, a true gem and if you don't have it then you really need to have it. You used to be able to download the game for free(although it had in-game ads unless you bought it), but this is sadly no longer the case

However, it can still be bought, which I highly recommend, because it's cheap and this game is worth 10x more than what you might buy it for. I actually bought the game for 20 dollars or so when it was relatively new, and I still replay it every now and then to this very day. The physics are so much fun and the story is really cool and dark.
It's a true tragedy that there was no sequel
