Play as one of four possible characters, all with there own special skills. Run, jump, fly, drive and shoot down enemy after enemy, before facing each stages Epic Boss. Then you get to choose what path the story takes, by deciding what mission to do next!
The objective is to walk through the end of each stage, shoot at every enemy that gets in the way, and fight the boss awaiting at the end. Unlike previous Contra games, such as Contra III, which featured overhead segments in addition to the regular side-view stages, all the stages in Hard Corps use the standard side-view perspective. Another difference is the player can now choose between one of four unique player characters. Like in previous Contra games, up to two players can play simultaneously, but they're not allowed to choose the same character.
The controls are similar to Contra III, but has been adapted to work with the Mega Drive/Genesis' three-button controller. The three buttons are used for shooting, jumping, and switching between weapons. While firing their gun, the player can switch between two shooting styles: one which allows for movement while shooting, and another that keeps the character still, allowing only to change their aim. The player can also jump down from certain platforms, as well as move on walls and ceilings like in Contra III. A new ability added to the game is a sliding technique performed by holding the direction-pad diagonally downwards while pressing the jump button. The character will be invulnerable while sliding and can even harm certain enemies. When controlling Browny, the player can also hover in the air by pressing the jump again during mid-air.
The multiple weapon system from Contra III has been revamped. The player can now carry up to four different weapons, as well as a supply of bombs. Like in previous games, weapons are obtained from flying capsule pods. This time the weapon items are now labeled "A", "B", "C", and "D", which will vary depending on the character controlled by the player. Each player begins with a standard semi-automatic machine gun, which will be replaced by the character's A-type weapon whenever it's picked. When the player loses a life, their current weapon will be lost. Unlike Contra III, the player's supply of bombs will remain the same when a life is lost.
Another unique feature to Contra: Hard Corps is the addition of branching paths that allows the player to play through a different set of stages depending on key decisions made during key moments of the game's story.
Set five years after the events of Contra III: The Alien Wars, an elite team of commandos called the "Unified Military Special Mobile Task Force K-X", also known as the "Contra Hard Corps", has been assembled to combat the rapid spread of crime and illegal activities following the war. When an unknown hacker infiltrates the city's security system and reprograms a group of unmanned robots to cause havoc, the Hard Corps are deployed to handle the situation. As the game progresses, the player will uncover a plot involving Colonel Bahamut, a former war hero, who seeks to overthrow the Government by developing new types of weapon using a stolen alien cell.
There are four possible paths in the game, each with its own final boss and ending, as well as hidden bonus stage for a total of five different endings. A sixth possible outcome also exists when the player sides with Colonel Bahamut when asked to, but the game will count this as a "game over" and not as a proper ending.
There are several playable characters. Ray Poward is a standard male soldier. Sheena Etranzi is a female soldier. Brad Fang is a wolf-like humanoid with a cannon for an arm.