I've been playing FPS shooters for most of my life. But I've had to stop. For some reason HL2 would give me headaches. Really, really bad headaches. I thought

I've been playing FPS shooters for most of my life. But I've had to stop. For some reason HL2 would give me headaches. Really, really bad headaches. I thought it might be the Engine, or me being tired. But I don't get headaches playing TF2 or Dystopia, both of which use the same engine. Surprisingly, Portal and Portal 2 didn't give me as bad headaches. Later games are hit-and-miss. Bioshock I didn't suffer. Bioshock Infinite gave me headaches within 15 minutes. And watching any Let's Play of a shooter gives me headaches within a minute. I've chalked the majority of it up to getting older. My gaming binges used to also give me headaches, but only after several hours. So I've had to switch to strategy games instead. But still, something about certain ways things are rendered or the FoV or framerate is affecting me and I wish I knew what it is.