Space Monsters

Space Monsters is a freeware futuristic top-down third-person shooter game developed by Psonic. It is also the first installment of the titular series inspired from the influences of other shooter games: Alien Shooter, Alien Breed, Crimsonland, Space Invaders, Alien Swarm, Half-Life, Doom and The House of the Dead.

Plot
This game sets in the spectacular year 2025, where the Long Passage Incident begins to overrun the whole surroundings of a headquarters with the dangerous invasion of the aggressive aliens who are under controlled by the evil mastermind named Roki (just before the replacement of his successor Syrax during the events of The Revival in 2026) after the examination of the strange creatures around the world. In case of that, General Baxter has reported that the other headquarters is in danger and search some human efforts against the hostile extraterrestrial species. The only thing he does is sending the respective operatives from few locations to prevent the disaster from making it complicated as the final hope of humanity just like what happens during the alien invasion.

Gameplay
Same as Alien Swarm. This game has retro-styled graphics, various role-playing game elements and top-down view.

Characters
Playable characters There are 3 playable operatives in the original version. In an upcoming expansion update, there are 3 extra playable characters. Non-playable characters Enemy characters
 * Billmore Hawkins (to be voiced by David Vincent in remake) - an American former War on Terror operative and assigned I.F. (Investigative Force) operative who resembles U.S. army veterans and has various skills in investigating cases. He describes himself kind and honorable.
 * Josh Celton (to be voiced by Matthew Mercer in remake) - a Scottish-born British special agent who had currently lived with his descendants. From the long time in leaving Europe, he is fully assigned to General Baxter for joining the special task force called Investigative Force as if there is the Long Passage Incident. He's also the best friend of Billmore.
 * Sam Ramsen (to be voiced by Kari Wahlgren in remake) - a detective and I.F. special operative who has a lot of job in doing her obligations like what she did in her childhood life and involving investigative cases, but a bit emotional.
 * Deck Homwell (to be voiced by Robin Atkin Downes in remake) - a Canadian technician for the Investigative Force.
 * Brake Andrens (to be voiced by Kiefer Sutherland in remake) - an American opposing force operative of the Investigative Force who helps together with Billmore and other fellow members, who are being dispatched to stop the alien invaders and their masterminds.
 * Rina Stock (to be voiced by Jennifer Hale in remake) - an Irish assassin who joined the Investigative Force to respond every cases caused by the alien invasion or other incidents.
 * General Baxter (to be voiced by Troy Baker in remake) - the founder and head of the Investigative Force who takes the military units to stop the alien incidents.
 * Roki (to be voiced by Patrick Seitz in remake) - the primary antagonist of the first campaign in the original release. It is the first mastermind and the predecessor of Syrax, which is responsible for controlling its alien minions with awareness to humankind and trying to take over the entire place in the Long Passage Complex.
 * Syrax (to be voiced by Robin Atkin Downes in remake) - the second mastermind and the spiritual successor who continues mobilizing the incidental work for another case after Roki's death, which must be avenged along with its destructive aliens.

Weapons

 * Armed Knife - a basic weapon used for closed combat but with a small amount of damage.
 * Pistol - also known as Handgun. It is a small semi-automatic portable firearm that deals a lighter damage when hit.
 * Shotgun - another firearm that fires a scatter of bullets and pumps afterwards.
 * Machine Gun - an automatic firearm that shoots rapidly to an enemy as a quick strategy.
 * Grenade Launcher - also referred to as Grenade Discharger. It is an 8-round explosive weapon that launches a grenade from a catridge in distance.
 * Rocket Launcher - another explosive weapon that fires a single rocket, which has more amount of damage to a wider area than a grenade launcher.
 * Sniper Rifle - a semi-automatic firearm that fires at long range as if the monsters are aware of a bullet.
 * Flamethrower - a mechanical incendiary devices used for controlling a stream of fire with low range.
 * Energy Cannon - a directed-energy weapon that fires a separated shots of laser beams, which are more powerful than a normal machine gun because it has a large amount of damage.

Equipment

 * Armor - used for protection.
 * Laser Sight (Crosshair) - used for guiding a target to aim properly.
 * Flashlight - an important equipment used for seeing anywhere in the dark even the generator is down.
 * Radar - used for navigating or revelaing anywhere through the map.
 * Medical Briefcase - used for restoring health with a large amount if the health of a player is lower.
 * Dynamites - used for placing near the top secret areas or enemy portals to let it explode completely.
 * Lives - used for how long you survived from alien apocalypse before you get down due to the failure of a current mission.

Bio-mechanical Implants

 * Health Implant - it gives you to increase 25 health points until 200 per limit.
 * Strength Implant - It gives you extra ammunition carriage of each weapon to reach the maximum number.
 * Speed Implant - it obtains how fast your speed is.
 * Accuracy Implant - if you get it, then you receive the target speed but functionally not featured in the game.

Keyboard Controls

 * ESC - Pause menu
 * Number keys (1-9) or Q and E - Change weapon
 * Up or W - Move up
 * Down or S - Move down
 * Left or A - Move left
 * Right or D - Move right
 * R - Reload
 * M - Toggle map (if you got a radar)
 * Ctrl - Toggle sniper scope (if you have sniper carbine)
 * F1 - Show game information
 * F2 - Debug message log
 * F3 - Restart level
 * F9 - Take a screenshot

Mouse Controls

 * Left button - Shoot/Attack
 * Right button - Melee

Trivia

 * The title itself is a reference of Taito's 1972 mechanical game, which is later changed to Space Invaders by Tomohiro's regime in 1978.