I have a hunch feeling that id had no real intention of implimenting such gameplay until HL2 showcased which is why we're seeing it so late in the dev cycle.
dont trust your feelings, as they're very wrong...
no really, id has implemented their physics engine right from start; it was also demonstrated in the E3 2002 demo, though it was far from finished (as just one zombie reacted with the ragdoll effect)...
what the autor means, is the demonstration by putting the boxes and let them collapse like Valve had shown with the barrels in their E3 demo and put so much attention on their physics stuff; as it seemed that everyone thought "uh, that's cool" id probably wanted to show their physics system in a similar way...
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everyone who finds a spelling error can keep it and use it as a base for his own errors
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