Beast Rizer 4

Petropolis 4 (ペトロポリス4) is a platforming video game produced by Burst Arts Inc. and published by Namco. It is the last 2D Petropolis game in the series. It was released in October 30th, 2000 in Japan and December 19th, 2000 overseas. It is available for the Nintendo 64 and PlayStation. The game even got remade for the Nintendo GameCube.

Story
Following the events of Petropolis 3, Thunder and his friends returned home to their respective islands. Summer vacation is still here, and yet there is nothing else to do for Thunder. He decided to play around at the park until he noticed a suspicious bed of sunflowers. He explored the seemingly endless field of flowers until he suddenly fell into them. Then, Thunder found himself in the "4th Dimension," as announced by a suspicious girl with green ears. Her name is Alice, and she claims that she is looking for her "other half." They do some exploring around this new dimension until they come across a chimera, but not like the ones Thunder is used to seeing: this one has the complete appearance of a beastman. The chimera, named Havoc, is on his mission to steal all of the sunflowers of the 4th Dimension in an attempt to return to his original form. Now, Thunder must seek the assistance of his friends from the 1st Dimension (his home dimension, according to Alice) in order to stop Havoc and his Wraith Beasts from stealing all of the sunflowers.

Playable Characters

 * Thunder Storminski: Plays as he did in Petropolis 3, but he can now used the Charged Surge, an attack introduced in this game.
 * Carla Fowl: Her gameplay is completely updated in this game. Now her attacks can be recharged after over-usage.
 * Mars Stanford: His gameplay was tweaked a bit to make himself as powerful as the other characters. He is strong only in nocturnal stages.
 * Grove Frasier: He was given a slight buff from the Petropolis remake. The water he uses can also come from rainy stages.
 * Chippy Nutcheeks: At some point in the game, Miyu assist her. She can use Miyu to attack at a long range.
 * Rick Ogami: He resorts to using his spear when in his beastman form. His monster form sees him using his claws.

Non-Playable Characters
Alice Emeraldsphere: A strange girl with green ears who resides in the 4th Dimension. She vaguely remembers her true past other than her "other half" leaving her. She has been searching for her half until she came across two beastmen: Havoc, who has later resorted to devouring sunflowers to be a normal beastman, and Thunder, who fell into the 4th Dimension from exploring the sunflower bed. She and Thunder decide to help each other with saving the 4th Dimension from Havoc and his Wraith Beasts.

Miyu: A baby Wraith Beast that was supposed to follow the orders of Havoc. However, when it emerged into the 1st Dimension, it suddenly lost its way around and ended up in the Eastern Islands. Chippy found it and cared for it for a while until one of the Wraith Beasts kidnapped and dragged her into the 4th Dimension. Miyu was able to free her from the monster's grasp and she thanked it for its help. Miyu then assisted Chippy for the rest of their lives.

Havoc Chimera: The primary antagonist of the game. A chimera beastman who lives in the 4th Dimension. He has a strong craving for the dimensional sunflowers, claiming to be the cure to transform him into a regular beastman. He has sent his Wraith Beasts to collect the sunflowers for him. Later it is revealed that Havoc was never a normal beastman; he is the son of Chaos Chimera, one of the most fearsome chimeras of the 1st Dimension who also fell into the 4th Dimension the same way Thunder did years later to escape the Chimera War. It is also revealed that Havoc has been tricked into stealing and eating sunflowers by Alice's other half, Silas.

Silas Emeraldsphere: The true main antagonist of the game. Silas is a boy with strange orange ears. He remembers being separated from his other half Alice after some event. He became determined to bring the two together again by using the power of the sunflowers. For this he tricked Havoc into thinking that eating the sunflowers can make him a normal beastman again. He even summoned the Wraith Beasts from their slumber in order to kidnap her. When the heroes finally get to fight him, Silas uses a black flower to turn Havoc evil. But this obviously fails and Silas resorts to fighting them himself. His boss fight has two phases: the first phase is where he transforms into his true self to fight, and the second phase is where he transforms every sunflower black and absorbs them to become a flower monster. He was almost impossible to defeat until Alice sacrificed herself by fusing with Silas.

Adelaide: The goddess of the 4th Dimension. She has ruled over the beings of this dimension until she was struck down during a war that took place many years ago. This caused her to be separated into two separate halves: Alice and Silas. After the two have successfully fused, she sent Thunder and his heroes back to the 1st Dimension after undoing the mess caused by Havoc and Silas. She even allowed Havoc to change his ways and benefit their dimension.