Portal's a hard game for me to give an unbiased opinion on, it's a game I've been replaying on a whim for well over a decade now, I'm quite fond of it. It's not the most challenging puzzle game in the world, just hard enough that you have to rub a few brain cells together at times but the solution's never too hard to grasp. It strikes a perfect blend of ominously dark and humorously witty, with GLaDOS being an iconic character both in voice and personality. To reiterate the "over a decade" part, Portal also holds a special, nostalgic place in my heart so it's hard for me to feel anything but positive about it.