The strategies get a bit more complex when you factor momentum into the portals. If you place two portals on the ground next to each other, and dive into one from a high platform, you will then pop out of the other into the air with a momentum boost, which adds a bit of a platforming challenge to the puzzles.

Where Portal starts to take a drastic turn from the traditional puzzle game structure is also where the most questions arise. For instance: Portal has a story that takes place within the Half-Life 2 universe, with an entirely new female main character, and features progression over the course of the game. So you'll start the game with nothing in your hands, earn your way up to a "gun" that shoots one portal at a time, then a version of that gun which shoots two portals at a time so you can connect them, then presumably later on an upgraded version that simulates the gravity gun power from Half-Life 2 (as was seen in the initial trailer).