According to Marvel Comics' lore, while trying to save his good friend, Rick Jones, nuclear physicist Dr. Robert Bruce Banner was caught in a blast from an atomic explosion. The resulting massive dose of gamma radiation altered Dr. Banner's body chemistry forever. Now, whenever the good doctor gets angry or frustrated, he turns into The Incredible Hulk, a huge, green superhero monster with massive strength.
Through the years, Hulk has amassed a number of foes, including the Leader, who has decided to conquer Earth because he figures it should only be ruled by someone of his superior intellect. To initiate his plan, he constructs a huge fortress within a savage forest and builds a vast army of battalion robots and genetically engineered mutants, such as lizards, slugs, cement-mixer men and sword-wielding Romans.
In addition, the Leader has enlisted the help of five boss character supervillains: Rhino, whose head butts can be lethal; Tyrannus, who fires thunderbolts; Absorbing Man, who wields a ball and chain and can transform into different substances; Abomination, who appears throughout the game and is almost as strong as Hulk himself; and The Brain, who releases an onslaught of smaller brains. Each boss (other than Abomination) guards the end of a level. Levels include City & Construction Site, Tyrannus' Labyrinth, The Leader's Fortress, The Leader's Interior and Final Confrontation.
If you haven't guessed by now, this game puts you in the title role, and it is your job to make Earth safe once again by making it past obstacles (such as spiky tusks and hover guns) while beating up a bunch of bad guys. Your appearance and abilities will vary among four different energy states. When your gamma energy is low and you are Bruce, you cannot fight, but you can access certain areas of the map not available to the others and pick up and fire a gun.
As Hulk, you can execute a number of standard moves, such as punching, slapping and headbutting. You can also grab and throw enemies and objects, such as stone pillars and jeeps. When you have upgraded to Super-Hulk, you can smash ceilings, pull off a sonic clap maneuver and execute a foot mashing technique. When your gamma energy is at its peak, you will Hulk-Out and become a savage, uncontrollable beast with immense power. To increase your energy, you must collect Gamma Capsules or Transformation Capsules that appear throughout the game.
You can find extra lives and extra credits in various areas within the levels, but they are usually hidden in bonus rooms or in places only accessible in Hulk-Out mode.