In IG, the player takes control of an interstellar empire on a 2D map. The game has multiple views: galactic, planetary, space battle. The main view is galactic, showing the explored space from the "top" with stars, planets, and fleets. Planetary view allows player to manage colonies by purchasing various buildings (e.g. residences, power plants, hospitals, factories) to improve them. Invasions are also played out in this view. Fleets consist of capital ships and fighters. Only flagships can carry invasion forces (made up of various tanks and support vehicles). Flagships are also the most powerful ships in the fleet. The player also manages research, diplomacy, taxes, and spies. Like the main screen, all battles (both space and ground) are in real-time. When encountering an enemy fleet, the game switches to the space battle view. Depending on the number of ships, they may show up individually or in groups. The player can order ships to move and fire. Invasions involve the attacker landing tanks to take out the defending tanks and any ground-based defenses.
The single-player campaign takes place in the 3200s and involves the Player Character Dante Johnson of the Galactic Empire being given command of a destroyer and three fighters to start, as well as three colonies. As the storyline plays out, the player's rank increases from Lieutenant all the way to Grand Admiral. Each rank unlocks more features and a larger map. The galaxy is full of both alien races and factions that broke off from the Empire. The main antagonist in the campaign is the Dargslan Kingdom. If the player takes too long to complete the "training" missions, he/she may find the galaxy already in Dargslan hands when the main portion is unlocked.
The sequel has improved graphics and three campaigns. However, none of the factions of the first game make it into the sequel. Additionally, space combat has been radically altered: fighters are no longer under direct control and are, instead, subject only to the "attack-defend" behavior slider. Tactics also matter much less here as opposed to numbers and firepower. Flagships have been removed, and any capital ship may carry a certain number of tanks. Also, unlike the first game, fighters are now able to form their own fleets and travel between stars, albeit at the minimum speed. Placing trading ports on planets allows the purchase and sale of alien ships and tanks. The three main factions in the game are the Solarian Federation (which appears to be the successor to the Galactic Empire), the Shinari Republic (a race of master spies and traders), and the Kra'hen Empire (a vicious extragalactic race known to collect heads of their fallen enemies; incapable of espionage or trade but also can't be spied upon). Many of the other races are, eventually, revealed to be Transplanted Humans, whose physiology was altered to survive on their colonies and who, eventually, broke away from humanity.
Now it has an open source remake written in Java found here.
The games provide examples of:
- 2-D Space
- Arbitrary Headcount Limit: In the first game, a fleet is maxed out at 28 capital ships and 180 fighters. However, the cap is not enforced when merging fleets. The sequel doesn't put a cap on the number of ships in a fleet. A flagship in the first game can only transport so many tanks. The sequel has each capital ship be able to transport a number of tanks, so a large fleet can transport a lot of tanks. However, if any of the ships are destroyed, so are the tanks they're transporting.
- Artificial Stupidity: The Dargslans always use max fleets of 3 flagships, 25 destroyers and 70 fighters, and they're fast and powerful enough that only top tier endgame quipment has a chance against them toe-to-toe. If you intercept them with even so much as a single destroyer, then order it to retreat as soon as combat starts, once the battle is over the Dargslan fleet will return to base to re-arm and repair.
- Design-It-Yourself Equipment: The sequel allows the player to put different weapons and systems on ship/station hardpoints. When upgrading weapons/systems, all ships of that type can be upgraded for a price.
- The Emperor: Kaileron was a mad Solarian emperor who had himself placed in suspended animation in order to be awoken to "lead humanity to glory" when the time came. The Shinari seek to revive him in order to sew chaos in the galaxy to make profit.
- The Federation: The Solarian Federation in the second game.
- 4X: The real-time kind.
- God-Emperor: The Kra'hen Empire is ruled by a God-Emperor whose will is treated as divine law. The player in the Kra'hen campaign is the Imperator sent to this galaxy to conquer it.
- Hard-Coded Hostility: In Imperium Galactica II, the Kra'hen faction (Absolute Xenophobe Blood Knight aliens from another galaxy) are always hostile and won't receive diplomats or traders, and if you play as them, you can't use the diplomacy, trade, or espionage options.
- Hover Tank: The most advanced type of tank propulsion.
- Human Popsicle: The mad Emperor Kaileron had himself placed in suspended animation until such time as his followers will deem his presense necessary.
- Humans by Any Other Name: The sequel calls humans "Solarians". Additionally, the Solarian campaign reveals that many of the "alien" races were originally human as well.
- Informed Ability/Informed Flaw: In the second game, the Shinari. In theory, they are weak at combat, and players are encouraged to make use of trade and spying to make up for this weakness. However...
- Informed Ability: While spying is effective, trading ships rarely visit planets enough to make up for the initial investment in ports and facilities, rendering one of the listed Shinari advantages much less powerful
- Informed Flaw: On the other hand, while the Shinari do suffer some combat weaknesses (fewer lasers, inability to use torpedos, missing some high end technologies) once they get cruisers, they gain access to possibly the most powerful weapon in the game: ship manipulators. This weapon takes over enemy ships, causing all sorts of havoc amongst enemy fleets, allowing a Shinari cruiser or above fleet to take on far larger enemy fleets. Additionally, their stronger economy allows the Shinari to compensate for their supposedly weaker ships by just building/buying more of them and overwhelming the enemy with sheer numbers.
- In Name Only: Since absolutely nothing carries over between the two games.
- Kung Fu-Proof Mook: Kra'hen in the sequel can't be spied on
- The Milky Way Is the Only Way: Played straight in the first game but averted in the sequel with the arrival of the Kra'hen from another galaxy.
- Somewhat defied in the first game in that the Magellanic Clouds and Andromeda galaxies are able to be visited.
- Older Is Better: In the first game, when you reach the rank of Admiral, you are given the most powerful flagship available. It's not buildable and is the last of the Leviathan-class flagships from the heyday of the Galactic Empire.
- Player Character: The first game has you play as Dante Johnson, a young up-and-coming Lieutenant with a tiny task force at his command, who can eventually rise to become the Grand Admiral. The sequel never names the Non Entity Generals of the campaigns, although your Player Character in the Solarian campaign can marry a Space Pirate princess in order to secure an alliance with them.
- Proud Merchant Race: The Shinari are all about business. In fact, they seek to destabilize the galactic peace because war represents an excellent opportunity to make a profit.
- Proud Warrior Race: The Kra'hen Empire as their goal is to dominate the universe, eliminate all other races, and collect their heads.
- The Sullep and Dargslan in the first game.
- Scary Dogmatic Aliens: The Kra'hen are an extragalactic race whose God-Emperor demands constant conquest and destruction of other races. Specifically, he wants the heads of his enemies delivered to him. They are so alien that no spying is possible against them (they can't spy either), and they refuse to trade with anyone. Given that they are in this galaxy now, it can be inferred that their own galaxy has already been conquered.
- Shout-Out: The name of the flagship in the first game is Thorin.
- Single-Biome Planet: Planet types in the second game are named as if they are these. (Desert, Barren, Volcanic, Forest, Grass, Rocky, Ice, and Mars-like.) Colony views of some types support this, others are more varied.
- Space Fighter: 6 types of fighters are available (depending on the research level) in the first game with various strengths and weaknesses. They're only useful against other fighters and weak destroyers (when used en masse). The sequel nerfs them even more, also removing the ability to directly control their actions in battle.
- Space Pirates: They occasionally show up to attack traders and raid colonies. They play a more important role in the Solarian campaign in the sequel.
- Spiritual Successor: Digital Reality's later title Haegemonia: Legions of Iron borrows much from the series. Additionally, Nexus: The Jupiter Incident is seen by many as an unofficial prequel to the series given its roots.
- The game itself to Reunion (1994).
- Standard Sci-Fi Fleet: The first game includes 6 types of fighters, 3 types of destroyers, 3 types of cruisers, and 4 types of flagships (1 of them is not buildable and is given to the player upon reaching the rank of Admiral). The sequel gets rid of flagships but adds battleships.
- Tank Goodness: Most vehicles used in planetary battles are tanks of various kinds: wheeled, treaded, antigravity.
- Terraforming: The sequel has Genesis-style devices that can be used to improve a colony to Earth-type with a flash of light.
- Tomato in the Mirror: Dante Johnson is revealed to be an android created as a last-ditch effort to save the Empire.
- Transplanted Humans: A number of alien races, including the Iberon, Godan, and Toluen, are revealed to have been human colonists subjected to radical bio-engineering in order to better fit into their new environment.
- Vestigial Empire: The Galactic Empire in the first game is in decline with a number of breakaway factions. Your task is to restore its former glory. By the time of the sequel, the Empire is gone, replaced by the Solarian Federation.
- War for Fun and Profit: The Shinari's ending has them resurrect a Solarian Emperor to create more conflict for them to profit over.