This first level is very easy, even on your first time.
For this difficulty you should wait in the cinema until you can see the entire roof of the first building. Start off and pause, switching to the ECM mine. Strafe to the left and fall off the side of the rooftop, rotating in midair to face the first grated door and opening it before you land. Open the next one as you continue to speed strafe. Move past the guard, fall to the right off the ramp and onto the lower one , prime the mine so that you throw it just as you're looking towards the security hub. and then pick up the pace to the left aiming towards the next door.
Open this door again as you run at full speed. Turn yourself so that you are facing the first railing as you sprint. Hug the railing tightly and you should successfully "ride" the railing and float over the glass where you would normally turn to descend the second half of the mini-flight of stairs. As soon as you are over the glass, strafe right, hopefully squeaking in between the layer of glass below. Luck Alert! Optimally, a guard will be opening the sliding brown door for you here, and you should be able to strafe past him, you should now be unarmed. Skip past the first elevator and rush into Cassandra de Vries' office to disarm her and grab the necklace.
Now go to the open elevator door and shut it behind you as you enter. Once reaching the bottom floor, run to the multicolored door on the right. Open it, and precariously hurl the ECM Mine towards the small computer monitor. Simply pray that the toss landed cleanly on the monitor. Luck Alert! Also hope that no guards shot you just before you released the mine. Otherwise, your throw will be off target by a ridiculous amount.
Continue on to open the sliding brown door at the bottom. Luck Alert! In the best of situations, all of the guards will move out of your way and clear a path to the elevator. The sliding portion of the wall that reveals the elevator should not impede your progress as well, although this also can be the result of the Perfect Dark gods of randomness (sp?) :) Now just open the elevator door to the research labs from as great a distance as possible.
