Konami appeared to have always wanted to try its luck in markets that are not created by Nintendo's consoles. Contra: Hard Corps is an attempt at doing - and it turns out to be quite a good one (despite the Sega Genesis's difficulty at penetrating a market already saturated by Nintendo's goods).
Officially, the story of Contra: Hard Corps is set some years after the canonical conclusion of Contra III: Alien Wars. While the world had been saved by Bill and Lance, the original duo of commandos, the consequences of the invasion, namely the introduction of technology derived from that of the aliens and the generally slow rebuilding of government establishments, had resulted in the world slipping into social upheaval and the rise of crime fueled by spoils of the war and committed by the disaffected.
Unlike the premise of the previous games, where the story was often essentially no more than an excuse to have the player unleashing bedlam on hostile forces that deserve the beat-down from the get-go, the one in Hard Corps actually has some semblance of plot development. It starts off with what seems to be the actions of yet-unknown covert operatives. Further exposition is obtained through the escalation of the destructive efforts of the faction that these operatives belong to.
Contra: Hard Corps offers different player characters who have actually different capabilities and even different weapons for the same weapon power-up. It was not the first Contra title to offer such, but it certainly was the first to officially do so.
(The previous Contra title to do this was Contra: Force, but this one was more of a spin-off and was incorporated into the Contra franchise due to marketing decisions.)
Each player character is capable enough of completing the game on his/her/its own. Also, despite their different sprite models (and thus different hitboxes) and different abilities and weapons, not one of them appear to be overpowered.
For example, CX-1-DA300, who is a combat robot, appears to have a smaller model and moves at the same speed as the others, so it would seem to have an easier time dodging enemy fire than the others. However, its setback is that it has a shorter jump, which it has to compensate for with rocket boosters that incidentally are not as easy to control as the simple leap that has to be done before its activation.
All characters have a sliding move that allows them to slip past certain enemies, especially bosses with attack patterns that cannot be reliably evaded otherwise. This sliding maneuver also happens to instantly trip and defeat certain goon-class enemies.
Another significant change in the gameplay is that player characters are now capable of storing up to four different weapons (five if the Smartbomb is to be included), each set unique to its associated player character. They can switch between them on the run, thus providing them with plenty of versatility and flexibility when dealing with different kinds of enemies and situations. Unlike the previous Contra games, the player character does not lose all of his/her weapons and reverts to the default pea-shooter when he/she gets K.O.'ed, but only loses whatever weapon is being equipped at the time.
Enemies in this game are a terrifically varied bunch, perhaps even more so than in the previous games. There are crazed robots/soldiers/monsters of all shapes and sizes, with different methods of attacks that can catch an unwary player flat-footed. For example, there are the usual, typically suicidal enemy goons who rush up to the player character without any heed of retaliatory fire, but these do so in ways and with animations that are so hilarious to watch compared to the seemingly mindless fools in games of yore.
Other than the ones that had been deliberately designed to be idiotic, the rest are decently competent in their pursuit of the player character; gone are the enemies who just pass by making shots of opportunity. The new ones, given the chance, will hound the player to the end of a stage if they are not gotten rid of quickly (or unless the programming of a stage simply kills off any pursuers at certain sections of said stage).
The bosses and sub-bosses in this game benefited from the peculiar 16/32-bit architecture of the Sega Genesis. While they appear to be animated quite simply, they are very well-detailed and often lurch about in manners that are hardly seen in their peers in games that are designed for a 16-bit machine. They also tend to warp the platforms that the player characters have to fight on in ways that would not have been possible on games that ran on less sophisticated hardware.
As a result, each fight is very suspenseful because the bosses resort to maneuvers that can cover much of the screen quickly, with hardly any blind spots, which had caused humiliating defeats for their predecessors on older platforms. Thus, the player often has to fight them out the hard way, i.e. with quick thinking and reflexes. (However, there are bosses that have blind spots in the game, but these compensate by switching them about periodically.)
One particularly memorable boss fight had the player characters sprinting ridiculously fast down a highway, while being hounded by an enemy character with a huge ego (and a big wonky-looking robot that he just loves to flaunt).
The reward for boss fights are concluding animations that are often very amusing to watch unfold - especially as their countenance gradually changes as they take more damage (and which may also change their attack patterns) and when they die in a very noisy and explosive way.
(That said, some of the bosses attempt to take the player character with them before they go down for the count, which can add a refreshing though not necessarily pleasant element of surprise to the gameplay.)
Contra: Hard Corps was perhaps the Contra title with the most numerous and visually distinct array of enemy models and animations then.
The stages that had been designed for the game are lavished with plenty of details, such as ruins from the Alien Wars, ruins that had been freshly made instead, plenty of wreckage and many flourishes of light (especially in the background). Perhaps in an attempt to show off the attention to detail, the screen had been designed to pan itself about in some cutscenes that unfold across certain segments of a stage that has them.
(Panning of the screen also appears to occur during gameplay, usually for scenarios where a transition of the screen is needed. This panning appears to have some glitches that are either exploitable or frustrating; in one scenario, a vertically rising screen brings doom to any player who is too slow to play catch-up with it, i.e. falling off-screen, while another had the screen panning horizontally, which the player can exploit in order to move his/her player character forward without the press of any directional button. However, this is only a minor glitch.)
Most importantly, the order of stages that the player plays through is no longer rigidly linear. In concert with the designers' effort to instill some sense of story development into the game, the player can make a choice - often a binary one - in certain moments in the game. These choices are not just one-off, forgettable decisions that result in a mere change in the type of stage played; the game actually keeps track of the player's combination of choices, and presents a different ending for each unique combination.
There appears to be some gaps in the plot development that do not follow the player's choices, especially in the mission briefings, though these gaps could have been filled anyway by the reason that for every stage/mission in the game, only up to two of four player characters would be undertaking it; the other two could have compensated for the events that led up to said mission briefings.
The music in this game is fantastically upbeat, making use of the Sega Genesis's hardware to produce some of the richest techno and electronic tunes ever heard in a Contra game then.
The sound effects in this game are just as heart-thumping as the musical scores. Like in the previous Contra games, every occurrence on-screen has a sound-clip that is associated with it. The Sega Genesis does a pretty good job of making sure that just about every sound-clip is accounted for, though there are some moments in the game where a sound effect of high bass obscures the others.
Like the previous Contra games, having a co-op mode for this one and playing it increases the fun factor even further. However, due to the different designs of the player characters and their different colour schemes (which are more often than not shared by enemy models as well), it would have been difficult to tell the two of them apart from anything else on-screen.
Fortunately, the game designers had likely thought of that and gave each of the player characters visually unique weapons; none of them shares a similar-looking gun. Closely knit duos would be able to know where they are relative to each other at a glance from their weapons-fire.
In conclusion, Contra: Hard Corps is a fantastic side-scrolling shooter, and is a gem among the list of games for the Sega Genesis.