Alien Invaders: The Tower Defense

It starts in your room. Stand on your spot, pull the trigger and a steel elevator builds itself around you, then rides 200 meters up a tower above a burning cyberpunk city.

At the top, alien portals open in the sky and the ships pour out. Destroy them with your blaster before they wreck the tower. Every hit makes the building shake and lean under your feet, and as it takes damage it gives way a little more....