Punch in your unique CPU code and, if it's correct, the screen will glow green. Get in the Gravity Lift, activate it and then you'll rise up to a keypad with a screen to the right of it. Pull the handle and then make your way around to the centre of the core. The lever's location is shown on the map above. You'll need to pull a handle accessible from the upper walkway overlooking the area to unlock it. When you arrive, the Gravity Lift leading to the centre of Reactor is locked off. Make sure you activate your Environmental Protection Suit before entering to give yourself the best chance of survival. The map location is marked by the cursor in the image above. That's the heavily irradiated area in the centre of the map, just down the path from where the Safety Override terminal was. When you have that code, head to the Reactor and make your way to the core.

In my run, the Medical digit was 5, the Research digit was 7, the Maintenance digit was 6, the Storage code was 4, the Flight Deck code was 2 and the Executive code was 9. If you're missing the Maintenance CPU, note that we've listed how to destroy it in the Executive walkthrough, as you'll only be able to complete it after unlocking the Grove Maintenance areas.

Our walkthroughs will show you the locations of these CPUs, so head back through each area if you're still missing one or two. To get the full code, we'll need to input the code numbers found in Medical, Research, Maintenance, Storage, Flight Deck and Executive.

System shock 2 full walkthrough