What’s surprising about the turret encounters is that they’re not purely puzzles: most of them can be conquered with speed, quick-thinking and makeshift cover, and they’re entirely freeform. In other words, they’re combat. It’s a refreshing change of pace from the thoughtfulness of the rest of the game, but if you do prefer to use only your brain, there’s always a clever way of avoiding being shot altogether.
Expert Narbacular Drop players and wormhole physicists might worry that they’ll breeze through Portal. But although it introduces its concepts to you gradually, it’s a complex equation by the end. The later levels involve bouncing energy balls, moving platforms, physics puzzles, weight-triggered doors and often require an impressive grasp of the subtleties of momentum. In fact, the last two chambers take 40 minutes or more each.