The group of bandits above were probably on their way to either attack a group of friendly stalkers or repopulate one of the bandit outposts I had cleared out earlier that day. Their presence was independent of mine and the fight between us had nothing to do with advancing the plot. I could have left them alone, been about my mission, and it wouldn't have mattered to the overall game. But as my impulsive attack got underway, I loved how intense and variable the combat was. I had to play through a few times to get it right (grenades are tricky) and each time it played out in a significantly different way - the bandits scattered in different directions, I missed a throw, or maybe a lucky burst caught me. And in STALKER, there's little margin for error.
Another encounter I had not long after does a great job of showing how much freedom STALKER gives the player. When you first come to the Agroprom Institute, you get a distress call from the STALKERs holed up inside, who are under attack from the army. My first instinct, which had worked for me on my first playthrough on normal difficulty, was to rush through the front gate and take the soldiers head on. It worked fine before, but on hard I got slapped around a few times. STALKER is not known as a forgiving game - you can take a couple shots, but that's it. Early in the game, when your armor is paper thin and your weapons are half-empty rubbish, you really have to think your way through fights.
So on my third try, I decided to exercise the freedom the wide open map afforded me. I went left before the gate and worked my way around the walled Institute, eventually finding a way through the fence on the back side. After offing an unwary sentry, I was in scott free. So I went up - scaled a couple ladders to the roof of the compound and worked my way back towards the gate. By then they had finished off most of the friendly STALKERs, but I had the drop on them from above. The fight was a mad scramble from rooftop to rooftop, using hit and run tactics, but the soldiers acquitted themselves well before I took them down. They had full length rifles against my shortened Kalashnikov, so they didn't let me off easy.
In most games, this battle would have been a scripted set-piece with a single 'correct' solution. But here it became a brilliant piece of emergent behavior as the AI tried to adapt to my unusual angle of attack. How many other games would let you take such an unorthodox path?
The best parts of the game are definitely the unscripted pell-mell fights like the ones I've described. Rob Zacny inspired these posts with his excellent piece about some similar STALKER fights - and I agree that STALKER gets weaker when it forces the player into a bottleneck. I stopped playing Shadow of Chernobyl the first time when I got to Pripyat, the finale near the end, because it just wasn't what I came for. I came to wander the wastes, scraping together money and gear so I could take on the next pack of bandits.
This sort of gameplay also makes me sad that all of the big budgets (and profits, let's be honest) in gaming these days is focused on highly directed and polished, movie-like experiences, instead of creating a dynamic system that can throw up surprises. I'd trade a dozen Call of Duty flashy action movies for a single game like STALKER that creates a world, then trusts the player to make their own game.