Laidlaw: Levels, creatures, characters and gameplay elements were in flux for a long time. Many ideas arose, became our favourites and then eventually fell by the wayside. The early plans for HL2 called for a story that spanned the globe and covered many days, but this would have meant discontinuities in space, time and Gordon Freeman's consciousness.
So we gradually tightened our focus on City 17 and the immediate area, and condensed the story so that all events could take place within a relatively short time span, without requiring Gordon to sleep, black-out or do any of those other things that usually mask a transition. Every time we tightened up the game, we'd shed a level, a monster or a character. This tended to make the surviving elements stronger and ensured that we made better use of them.
Lombardi: The physics festered their way into the game through the results of our play testing (which we do for months before any QA testing begins). Ravenholm, the original home of the 'physics part of the game' occurred a bit later in earlier versions, and it was the only place you had the gravity gun. But, as more and more testers told us this was gameplay they enjoyed (and we could start eliminating fears of being compared to bad experiments with physics in games), the closer Ravenholm moved to the start.
Laidlaw: Ravenholm and the gravity gun co-existed in our minds for a long time. The saw blades didn't appear until we'd spent some time in Ravenholm looking for things to throw...
Laidlaw: We tried not to force it: in the first Half-Life, the humour tended to be situational and fairly bleak, very much a part of the environment. The setting of HL2 was, if anything, even darker. However, instead of trying to cram comedy into it, we waited for opportunities to arise. We also had to be mindful of the fact that obvious gags would tend to jar people out of the game unless it was a seamless part of the experience; and at the same time, prepare for the fact that some people would not share our sense of humour. Even people within Valve disagreed about the comedy value of certain scenes. So, we tried not to overdo it; on the other hand, when it seemed to come naturally, we didn't force ourselves to censor it either.
Laidlaw: All the characters have evolved a bit to make the most of the skilful actors who portray them, but none are based on real people. We had a very good casting agency in Los Angeles who took our character descriptions and sent out casting calls. In some cases we had names of actors we thought would be ideal for the parts, although when we started on Half-Life 2 it seemed fairly unlikely that any of them would be interested in working with us. Robert Guillaume was our first choice for Eli from the very first time we talked about casting the part - the casting agency went and asked him directly.
THE CRYING COUPLE
Laidlaw: The germ of that idea came from a couple who appear both in Nintendo's Zelda: Ocarina Of Time and Zelda: Majora's Mask - oblivious to their surroundings and totally absorbed in each other. I wanted to do a darker, City 17 version. It was easy to summarise the idea, but difficult to convince people it was worth the production costs. While all I had to do was write a few lines of dialogue, someone else had to pose and animate them, set them up in the level, make sure they were invulnerable to playtesters... All that added up to quite a lot of work for quite a few people and is indicative of how much thought goes into even the smallest scenes in the game.
ALYX AND DOG
Laidlaw: I sympathise with people who wanted more interaction with Alyx during Half-Life 2. I was happy with where we ended up on this, but I'm also glad now that the expansion pack Aftermath is giving us the opportunity to revisit some of these partially-realised ambitions.