You will pick up Transformers: Fall of Cybertron right where War For Cybertron left off; in a ship leaving Cybertron and heading for a warp that will lead somewhere out of system, hopefully somewhere safe. But the Decepticons have other ideas, and they will almost immediately launch an attack against your ship. You will play as Bumblebee in this first tutorial-style level. You will have no choice for now but to stand by and watch as the large, snake-like appendages strike out at your ship. As one of the drills smashes its way into the hull, Bumblebee will fall back to the ground and lose conciousness. You will be awakened by some fellow Autobots after the worst of the attack. Follow the little glowing robot around using the right stick to proceed with the tutorial. If you like the standard controls, press "Yes," but otherwise hit "Noo" for inverted controls.
Afterwards, the Decepticons will launch an attack through the front hull of the ship. Shoot them from your prone position, and then hop up as more rush in through the front windshield. Mow them down with your machine gun, going for headshots when possible. After the attack, Megatron will beam his presence into your ship and threaten to tear your ship apart if you continue on your course. Optimus Prime will leave to fight the Decepticons on the bridge, leaving you and the rest of the Autobots to defend the bridge. The defense network will go down soon after, though, and this will leave Optimus defenseless if you can't get the Teletran to the power source immediately. Grab the power node from the console to the left, and then follow the Autobot out the door to the left. Round the corner as one of the enemies explodes, part of the collateral damage that is wracking the ship. Follow the surviving Autobot over the debris in your path ahead, hitting A (assuming you're playing on the Xbox 360, X otherwise) to leap over the fallen support columns in your path.
Proceed through the door ahead and into the next room, where you will encounter more Decepticons. They will flee as your allies pry the door open, but launch a counter-attack when you enter the room. Another of the snake drills will punch through the wall, but you will be saved just in time. Leap over the gulf ahead by hitting A and then quickly following it up with a tap of LB. Proceed into the room ahead and plant the energy core into the power source to reactivate the defense systems. The door in the center of the room ahead will open for you. Proceed inside of the room and click in the right stick to use your melee attack to bash the lift free of its confines. Ride the lift to the defense tower. Along the way, you will see Decepticons ravaging the Autobot troops and generally wreaking havok on the ship. Don't even bother wasting the ammo to fight back the Decepticons, as you won't be able to kill them before the lift moves on.
When you reach the top of the lift, exit the room and proceed out onto the bridge towards the defense tower. It will begin to explode and erupt into flame as you approach. Hold LB to sprint through the flames and then grab the glowing cube on the other side to recover health. When you enter the next room, prepare for a firefight. Enemies will be dug into the cover in the center of the room and the left side of the room. Attack them from afar when they poke their heads out of cover, or charge in for a few brutal melee attacks. When they are all gone, proceed into the hall ahead and rush the enemy at the control panel by hodling LB before hitting the melee button. Use the console to bring the defense tower online and repel some of the Decepticons. But where is Optimus? Looks like he's taking on Megatron on the bridge. You have to get there to back him up fast!
As you fall to the lower floor, you will jog your alternator back into place and enable transformations. Take this opportunity to transform by hitting the left stick, and then use the LT to boost down the exploding path ahead. Steer clear of the explosions and follow the arrows. When you receive a warning that you need to jump, tap A to jump even in your vehiculatr form. The rest of the Autobots will greet you ahead and usher you through the door. Follow them down the narrow hallway and into the makeshift defense center. Grab the energon cube inf you need it, and refill your ammo before heading into the next room. The Autobots will give you a Rocket Launcher. Pick it up and rush into the room ahead. Enemies will be to the high left and the low right, but you can easily dispatch them by holding LT to lock onto them and then hitting RT to send homing rockets straight at them. If you need more rocket ammo, you can always retreat back down the hall from which you came and scavenge some from the ammo pool near the rocket's spawn. Head back up and finish off the rest of the enemies.
In the next room you'll find more rocket ammo, so grab it all before rushing ahead to assist Optimus. The Autobots will cover you as you rush ahead. Sprint towards your waypoint, which will be floating all the way on the other side of the battlefield. Sprint behind the central cover point, bash the two enemies with your melee attacks, and then rush into the room and to safety on the other side. Note that there is ammo and health scattered to the right side of the battlefield if you find yourself running low.
Spoiler Alert!
Once Bumblebee has squeezed his way to the other side of the hole in the ship, he will be struck by Optimus and flung off of the side of the ship. You will have to hold forward on the analog stick to crawl towards Optimus. Megatron has him on the run, and he points a giant cannon at Optimus to finish the job. Quickly crawl forward and leap ahead to save Optmus, taking the cannon fire yourself in the process.
End Spoilers
Thus ends the first level of Transformers: Fall of Cyberton. With that unsuccessful escape attempt, the Autobots will have limited time to build one last escape ship and use the last of the planet's energon to fuel their desperate escape.