It's also well within your character's means to jump on to ledges and crouch under low areas to creep through the most inaccessible looking gaps. This allowed the level designers to increase the interest which adds an extra dimension to exploring. If there's a gap, you should be able to somehow crawl or jump into it but don't expect these acrobatic feats to be particularly easy.
The actual engine that looks after the levels has been improved. Where as Doom levels were flat 2-D maps extruded into a third dimension, Dark Forces is made up of proper 3-D levels.
This means you can walk under bridges as well as over them. There is also a superb multi-storey
level which is a bit like a cross between a hollow car park and an arena. It has lifts that will take you up
and down the levels and there are Storm Troopers everywhere that will shoot you from adjoining walkways.
