When I first bought half-life when it came out years ago, I looked at the box to see that WC 2.1 was on it, and it had that statement design your onw worlds for half-life' and I just thought 'wow, I've never heard of such coolness in a first person shooter game before'.
When I started mapping, it didnt occur to me about half-life dimensions and I had absolutely no concept of player scale, so everything was over-large. I also used the carve and hollow tool alot because I thought that you had to! ... Man, those were the days...