The year is 2020...

The human race is under attack by some unknown race.
All survivors MUST be transported to space, as a last ditch effort to preserve humanity.
All space vessels have regroup on the Earth's moon.
Many bases have been constructed.
These bases are the only hope for humans to repopulate and someday take back Earth.
The moon has remain undisturbed ever since The Evacuation of 2016.
Much progress is being made, and humans are slowly building a way back to Earth.

The year is2026, and a message was received at YOUR base at around 1:00 Earth time...

THE ALIEN RACE HAS DISCOVERED OUR HIDING.
THE BASES ARE COMING DOWN 1 BY 1.
ALL HUMANS BEING TERRORIZED.
NO CHANCE FOR ESCAPE OR SURVIVAL.
ALL HOPE IS LOST.
FINDER PLEASE TAKE PRECAUTIONS.
GOOD LUCK AND GOODBYE.

Your people were shocked by the report. Soon enough, the aliens began to invade your crater base. You are Earth's only hope for survival. If you succeed, the alien race will soon retreat and humanity can be saved. If you lose, the other moon bases will soon fall to the alien scum, and all hope is lost. Good luck.

Hurry up! You must get inside and prepare for the Invasion!

Once inside, you have four options:
1.Grab the rockets off the weapon table
2.Go out the door directly beside it and start demolishing aliens with gunfire
3.Take the teleporter to the first floor
4.Go to the roof from the door on the far side.

If you choose the teleporter, you will find yourself in the tunnel room first floor.
You can then go outside, go through the tunnel in the floor, or break through the blue shield and crawl through the vents(Humans only).

If you took the vent, it would lead you to the 3rd and final room, the room of defense.
It is completely sealed in from alien attack except for the shield door and the teleporter that leads to the roof.

Take the teleporter from there and you will return to the roof and you can return to the first room or take the moon rover.

Here is a view of the underground tunnel and the first room turret

Better view of the roof with a space shuttle resting on top. The shuttle is inactive, but contains a medkit at the top for health recharge. A secret teleporter can be seen on the mountains to the right.

Take the teleporter and you will find yourself inside of a ship with a surprise weapon in front of you.

MAKE SURE that you wait before going back so the out of bounds countdown can restart or you'll die.

The UFO where the aliens spawn.

A platform that can be reached by jetpack. It contains a sniper rifle.

Special thanks to Brady, Keaton, and Riley who helped me test this out :)