i have watch a gameplay video with john romero (one of the founders of id software) as guest,one or two weeks ago.
he said some rly good stuff about mapdesign.
one important point for singleplayer maps, which i if i think about it have seen in some et maps too
is the reuse of mapparts.
lets take a look at goldrush as example. the first attackers spawn is usefull the whole game and is also the end point for the truck.
on adlernest its the same ,its still a valid route for the obj run.
its smth that i miss , currently. we often have spoken about the tunnel mapfeeling.
there are rly cool ways for this stuff with todays engine opportunities .you could let collapse the bridge on LB as example,and reuse this way the first stage(yes a kind of levelusion),smth like this works in sp games rly well
and give the player the feeling that all have effects on the map , also i think its much simpler for the human brain to learn maps this way.
hf.