The mandatory PC games are the following, be sure you have steam: -Civilisation V - A turn based strategy where you have to take over the world starting at the beginning of recorded human history -The Half-Life 2 trilogy (HL2, Ep1, Ep2) - These Three games (well 1 and two halves) is a genre defining FPS experience on PC. Beware jump scares -Day Z or one of the many Zombie sims - I personally don't enjoy this multiplayer open world zombie game but people consistently insist I get it. Same with Arma. -One of the many free to play MMOs- be it Star Trek online or Warframe else these terrible games can be fun to lose your life in.