glaDOS is back! The insane computer that put you/Chell through a deranged maze of death traps in order to “test” you has been resurrected years after she was destroyed. And has reconstructed the lab with even more tests to make you think.
One of the most original and clever games ever (yes, I know the portal idea came from another game, which was fantasy based, but the execution of Portal was what made it so fresh). It had a great sense of humor and personality. Valve said it stunned them how emotionally attached people became to the game. It really set off several memes when it came out.
From what I have been reading, it sounds like the sequel promises a lot more cool stuff including a new sidekick AI that helps guide you through the game. Can’t wait!