I was about to buy it on Steam and it turns out that it is free if you already own the originals. Sweet!

I’m old enough to have been stunned by games like Cybernoid and Exolon (oooh, so many colours and sprites and explosions), Elite (damn, actual 3D wireframe spaceships!), Driller (wow, actual solid 3D at 0.5 frames per second!), Wolfenstein (actually playable 3D, with sprites), Doom (this changes everything), Quake (full 3D, nothing can improve on this), all the Half-Life franchise (you can also have a story to go with the shooting? who knew?), Portal, Portal 2 and The Talos Principle (puzzle games can have riveting stories) and finally Skyrim (damn, this thing is huuuge!). So yeah, I’m old. :-)

I find Half-Life and Portal are some of the best games ever made regarding world building, story telling and general addictiveness.

I keep coming back because I’ve never found any other game like those.