Wow, 2001 is full of great titles! In 2001 I was still playing PC games and Serious Sam was one of them. I really love the series and played the second one on PC too until I finally went full console gamer.
Have you seen this Talos Principle first person puzzle game Croteam did with the Serious Sam Engine?
I got this quote from Croteam's Gamescom recap: "And don't worry, there will be Serious Sam 4 after Talos and it will rock!" I can't wait!


