A guide on gamefaqs.
Always destroy all Cameras and Computer Nodes that you find. This will lower level security. Doors/switches etc. that say "blocked by level security" will all work when level security = 0% (and some will open when security drops to around 10%).
On each level is a Cyborg Conversion chamber. A switch nearby will reconfigure it to heal you when you are killed, instead of turning you into a Cyborg.
Some lit panels flat on the floor are elevators. Step on it to activate.
Each Cyberspace Terminal leads to a different enclosed area. You will have to complete the area for each different Cyberspace Terminal that you find.
If a door is "broken beyond repair", you cannot ever get through.
Many levels cannot be completed on your first pass. You will have to continue up to other levels and come back later.
No level is ever completely "clear" of enemies. They continue to reappear. Always be on your guard.
Some elevators will not operate ("power diverted to ...") until certain tasks are complete. If you are stuck, it is because you have failed to: