Your adventure begins in the Jersey Town square. In this square there are the entrances to the six areas of the game. Their entry is signaled by the rotating Giant K-Tokens floating in the air. The Giant K-Tokens at the entrance of the areas are transparent the first time you enter and become solid as you complete the levels of that area. In each area there are two regular levels, plus a hidden bonus level, accessible only after reaching a certain power level. You will necessarily have to face the two normal levels in a predefined order. The initial area is the same for both levels, but only after completing the first one, will the other become accessible. The accesses to the two levels from the initial area are marked with appropriate signs. Furthermore, when you have obtained enough Giant K-Tokens, other areas will become accessible, directly from the square. The only exception is the last area, the Knarf's Forest. You can access it with a rocket, which will appear in the center of the square when you have completed enough levels. To access the second part of this area, reaching the final confrontation with the mad scientist, you must first obtain all the Giant K-Tokens from the previous levels.
Jersey Devil can run, jump, hit enemies with his tail or punch, as well as be able to pick up or push certain items, or use his useful gliding ability. In each level you will have to fight your way, avoiding the dangers and defeating the enemies you find along the way. You will also need to collect various useful items to proceed, such as pumpkins that will earn you extra lives, the value of which is indicated at the top left of the screen. Many of the items are kept in boxes that you will have to break by jumping on them. Sometimes, to proceed, you will also need to find the five letters K - N - A - R - F, to get a "Golden K", which will allow you to open the doors marked with the appropriate symbol. These letters are sometimes well hidden and you have to look for them. Other times, to continue within a level you will have to activate special switches or solve some small puzzle. Your life energy is represented by the purple bar at the top, in the middle of the screen. Whenever Jersey Devil is hit by an enemy or touches something dangerous, he will lose some life energy. When your life energy runs out, you will lose a life. You will also immediately lose a life by falling into the void or into the water. Your number of lives is shown at the top right of the screen. If you lose all available lives it's game over. At the end of each level, you will have to defeat a boss to complete it. These are usually creatures mutated by Dr. Knarf or his assistant Dennis Pumpkin Head. After defeating it, you will automatically return to the city.
Inside the levels there are also special nitro boxes. By breaking them all, you will get a nitro vial, with which, after defeating the boss, you can blow up the laboratory, obtaining a power increase. A counter in the lower left corner of the screen indicates how many nitro boxes are still present within that level, while another indicator in the lower right corner shows your power level reached. Finally, in each level there are two hostages to rescue. The hostages are prisoners in cages and you can free them by hitting a special winch. Freeing them will increase your play-through percentage. There are 32 hostages in all in the game. By increasing your power level, you will be able to access bonus levels, where you can find many extra lives and more hostages to save.
Between one area and another of a certain level or after defeating the boss of a level, before returning to the city, you will be given the opportunity to save the game. When you save, the percentage of the game you have completed will also be shown. To complete the game 100%, you need to complete all levels (including bonus levels), as well as break all nitro boxes and rescue all hostages in each level. Of course, even after completing a level, you can still enter it if you wish. This is useful in case you have previously neglected to break some nitro boxes or save some hostages. By completing the game 100% you will be rewarded with a better and longer ending sequence.
The PAL version of the game has some differences from the NTSC version, in particular:
- Some graphics, such as nitro boxes are different.
- There are no hostages to rescue.
- It is not possible to save the game between one area and another of the same level, but only after completing a certain level.
- There are no cutscenes in the early stages of the game explaining the main moves the character can perform.
- Orange pumpkins help increase Jersey Devil's health and are only counted when his life bar is already full.