Whenever you go near an open door, or you pass through one, always close it (unless a teammate is right behind you).
The reason you do this is because of how the AI responds to obstacles when they're in a passive state. They'll simply reroute and go somewhere else if they hit a soft wall or a door, so closing every door you pass in turn limits the amount of enemy movement.
Also, I have a friend (once I know his @ I'll @ him) who pointed out that your Op's left thumb has blue bars, they'll turn red and grow when you're being spotted or chased. Pretty neat feature to keep an eye on if you play without audio-visual cues
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