Alien Hallway

There's a hallway, and there are aliens in it.

Alien Hallway is a strategy game developed by Sigma Team (the makers of the Alien Shooter games). Your task is to command a squad of Space Marines to fight to the other end of the hallway--which is, of course, filled with aliens--and destroy the aliens' base before they can do the same to you.

Tropes used in Alien Hallway include:

One Hundred Percent Completion: Getting five stars on every level earns you a Steam achievement.
Alien Invasion: The first planet you have to defend is Earth.
Cooldown: Represented by a greyed-out section on the icon that gradually drains away. You can purchase an upgrade to reduce the cooldown times.
Elite Mooks
Every Bullet Is a Tracer
Excuse Plot: The plot, in a nutshell, is "Aliens are bad. Shoot them."
Fire-Breathing Weapon: Your basic Flamethrower unit.
Frickin' Laser Beams: The weapon of choice for the strongest unit.
Gameplay Grading: Your performance on each level is rated from 1-5 stars, and you get more money for higher ratings. There's also an achievement for getting five stars on every level.
Giant Mook: In the later levels, some of the aliens have Mini Mechas to tower over the battlefield.
The Greys: The aliens.
Mini-Mecha: Worn by the Giant Mooks on the third planet.
Mooks: Armies of alien mooks.
RPG Elements: You earn gold for completing missions, and you can spend it on upgrades.
Secondary Fire: The flamethrower, shotgun, machine gun, and laser gun units can all throw grenades as well; a grenade icon pops over their head when it's available. A variant of the trope, in that the regular attack is automated, and only the secondary fire has to be manually activated.
Space Marines
Suicidal Overconfidence: The AI's job is to advance toward you at all costs, even if they're hopelessly outgunned.
Suicide Attack: One variety of Mook is an alien with a bomb who runs toward your guys and blows himself up.
Worker Unit: Engineers, whose job is to gather energy so you can create more units.