Wario Land 4 is the fourth (fifth, counting Virtual Boy Wario Land) game in the Wario Land franchise. Wario Land 4 was released for the Game Boy Advance on August 21, 2001 in Japan, October 1, 2001 in North America, and November 16, 2001 in Europe. The game was developed by Nintendo R&D1 and published by Nintendo. The game was largely similar to previous iterations in the franchise, starring Wario on a quest to gain more treasure.
Wario is reading the newspaper and stumbles upon an article about a pyramid in the middle of the jungle. The piece discusses a legend which has it that Princess Shokura, who ruled the pyramid, was cursed by a greed driven "Golden Diva." Upon reading this, Wario jumps into the Wariomoblie and rushes to the pyramid motivated by his own greed (as he knows the pyramid is filled with treasure).
After the Golden Diva's defeat, Wario takes all the treasure and runs away alongside The Professor and Princess Shokura (who is currently in the form of a cat). Wario escapes the pyramid right before it collapses and the 4 treasures surround the Princess and return her to her true form. She kisses Wario and flies away. Wario takes his treasure and drives away in his car, remembering his adventure.
The gameplay is much like that of previous Wario Land games. Wario can be altered by certain enemies to take on different forms and gain different abilities. However, this time he has a life meter, meaning that if he takes damage and does not change forms, he will lose health. Losing too much health will send him back to the hub area without his treasure. To complete a stage, Wario must step on a frog statue to activate a time bomb. Once he sets off this timer, he must return to the entrance before the timer runs out. If it does run out, Wario will start losing his coins. If he loses all of his coins, he will be thrown out of the stage.
The player is offered a certain degree of choice as to which levels they want to play first. The central chamber that Wario finds himself in acts as a hub and its four passages lead to the different themed areas of the game. The themes are horror, nature, toys, and an industrial themed area. Wario can travel to any of these themed areas at will and inside each one is 4 different stages, with the final one being the boss battle. Also located in every passage is a mini-game area which can be used to earn special coins. While Wario can choose any passage he likes at any time, he must still complete the four stages located within in order.
As for the bosses themselves, they can only be reached with the help of four gems. One gem can be found in four pieces on every stage. Once Wario finds all four pieces and leaves the stage he will get to place it in the door sealing off the boss' lair. Collecting all four gems from all four stages in that particular passage will permit Wario to gain access to the boss, as well as a store run by a character who bears strong resemblance to Mr. Game & Watch. At this store Wario can purchase items with the coins won from the mini-games to help him during his fight with the boss.
Along with the collectible treasures found throughout the worlds, there is a single compact disc hidden in every stage. Once this disc has been located, the player can listen to it in the music room located in the main hub. Each of these contains a bizarre musical composition and a simple but equally bizarre video that plays along with it.