Final Fantasy VII/Mako Reactor no. 1

The adventure begins
The opening cinematic leads us, thrillingly enough, right into the action. At the very beginning, you're controlling an Ex-SOLDIER, now employed by AVALANCHE, who gets to try out this newfangled combat interface right on. The first few soldiers are not too difficult to deal with: Just hit them with all of your might. In the reactor, you will also meet mechanical things: Brute force works wonders here, as does the Bolt magic. You can pick up handy things like Potions from the enemies you defeat. There's really nothing too difficult in this chapter; Learn the basics of the game interface, learn to fight, that sort of thing.

The first few rooms are quite straightforward. Your party, for most the rest of the chapter, consists of Cloud and Barret, both of whom you get to name, too. The only notable thing on the few first rooms is on a room to south: a chest holding a Phoenix Down.

Along the way, you will learn how to climb ladders, operate buttons, and like. You'll eventually reach the actual reactor room. On the floor, there's a Restore Materia and a save point. So this is a good place to learn how to pick up items and save the game.

A mission would be nothing without a good, big, warm-up fight. As soon as the bombs are ready to get tripped, a really big nasty thing shows up.

(Notice the similarity of tactics with the first boss in FF6...)

The boss leaves an Assault Gun, which Barret can use, and is better than his default weapon. The time bomb is set, and you now have 10 minutes to go back the same way you came.

Along the way, you'll run into Jessie whose foot seems to be stuck. Talk to her and help her to get loose again. If you missed her and get back to the rest of the gang, you still probably have plenty of time to get back and there again. Once you're out, the reactor blows up.

Going to Sector 7? The train just left.
After you escape, you and the rest of the AVALANCHE split up. There isn't much to see here, but you actually do get to meet Aerith for the first time. You can buy flowers from her.

When you finally head towards the train station, you get surrounded by soldiers, who, as the beginning of the adventure showed, are quite trivial to defeat. Eventually, the torrent of clowns ends, and you leap from the bridge to the roof of the passing train, conveniently right on the right car too.

After you get back to the station, head left, where you find, among other things, a savepoint. The Sector 7 slums are further to the left.