>>284964959
You'd be better off if you knew what was going on, but you'll probably still be fine if you haven't. They've been free to play for the past 2 months though, so if you were going to play them, you probably should've done that already.
https://store.steampowered.com/news/57848/
>>284967354
Even the original Half-Life is fine other than Xen. There's always Black Mesa if you'd rather play a modernized version of that though.