Don't tell anyone, but some of Portal's best dialog, the stuff about the importance of your weighed companion cube, came from writer Eric Wolpaw's readings of some "declassified government interrogation thing."

From that, he learned "isolation leads subjects to begin to attach to inanimate objects." So when Kim Swift and the rest of the small Portal team at Valve, which was never larger than ten people, were trying to make players drag "this stupid thing" (Swift's exact words) all over a map, Wolpaw had an idea.

His solution? Have a piece of dialog that implied the box was the player's only friend in the world. "After that, no one ever forget the box," Swift noted. "When all else fails, great dialog really was a great tool to give hints to players."

Making the Player Smile
"On its own, the [Portal] gameplay would be alright. Honestly, a little on the dry side," said Swift, emphasizing the importance of clever writing in the beloved title.

"If you're writing a funny game, first of all, god help you," admitted Wolpaw. "It's unpleasant, funny dialog is funny [to the writer] once, maybe."

"We wanted players to feel genuinely happy and leave the game smiling," explained Swift, who noted that "a lot [of the decisions] came out of our constraints...The cost-happiness ratio of putting a song with scrolling text was really high."

The End, Boss Battles
But, apart from a clever song, how to actually end the game?

The team constantly struggled with Portal's conclusion. "What in the world will a boss battle look like in a weird environmental puzzle game," Swift asked.

According to her, the original conclusion with "James Bond lasers" chasing after players was quite boring. The second attempt, jokingly called "Portal Kombat," had too much action, with players trying to redirect rockets while avoiding turret fire.

"High intensity gameplay sucked, that sucked so bad," said Wolpaw. "No one paid attention to [main boss] GLaDOS or any of her dialog. The vast majority of our playtesters were just frustrated."

"The final attempt was to have a chase sequence [with players going after a fleeing GLaDOS]," Swift explained. "[It was] supposed to be action-packed. Instead players were just walking around and confused."

"This [attempt] failed in every way possible," noted Wolpaw. "It's funny to us now, but we were desperately screwed at this point. After ten years [in development], Team Fortress 2 was about to beat us out [the door].

And then, like a portal opening before them, a solution magically appeared.

"Playtesters felt [the fire pit puzzle] was both climatic and satisfying," Wolpaw explained. "It was about the easiest puzzle [at that point in the game]"

"It had time pressure," noted Swift. "Time pressure makes people think something is a lot more complicated than it really is."

"We'd been holding onto the idea of a complex puzzle at the end," Wolpaw noted. "[But] instead of getting fancy we just had a [simple puzzle and a] timer counting down."

This solution also had the added benefit of creating an hard limit for the amount of dialog needed, lessening Wolpaw's work considerably. "It was really cheap to make [the poison gas]," he added.

Multiplayer
"Oh my god, portals in deathmatch," Swift exclaimed when asked about the possibility of a multiplayer Portal. "Honestly, it's less fun than you'd think."

Fan Questions
Following their talk, Wolpaw and Swift fielded numerous questions from fans. The highlights were:

Q: Given the success of Portal, how will you approach the next game, as most of the game design was based on your team's limitations?

"I don't know. I'm scared," responded Wolpaw. "Seriously, I don't know. I..don't know."

Q: Is GLaDOS still alive?

"Did you not listen to the last song?," laughed Swift.

Q: Why does GLaDOS have an incinerator in her room?

Aperture Science ensured GLaDOS's trappings could destroy her if she ran amok, Swift revealed.

There was even a red phone in there in case of an emergency, elaborated Wolpaw, who noted that it must have been pretty ineffective. In his words, the folks of Aperture are "half geniuses, half morons."

Q: Is the main character a cyborg?

"She is not a cyborg," the duo clarified, noting that her "ridiculous cyborg shoes" led to some confusion.

Q: Why were both characters female?

"[Valve co-founder] Gabe [Newell] came up to us...and said 'well, why don't you make [the main character] a girl?'" Swift responded.

"We knew an actress," Wolpaw remarked of GLaDOS. "And casting [reliably] is hard."

Q: Lastly, and most importantly, why were the portals in the final game more orange than those in the initial trailer?

"We liked orange better than red," Swift disclosed with a laugh.