Rumble Robots was a children's collectible card game sold in starter decks and booster packs circa 2001. The premise is based around warring factions of sci-fi robots. There are two sides: a blue team of good guys, and a red team of bad guys, each lead by a robot king. The blue king is King El Smasho and the red king is King Slugnut. The cards themselves are called Power Cards and contain bar codes for interaction with Rumble Robots toys. Each card has a "power level" from 1-5 which corresponds to both its rarity and relative usefulness in the game. In addition, there are "platinum" cards, more powerful than level 5 cards. One expansion set was released, "Rumble Robots: Invasion", which focused on the two king characters as well as adding a further rarity level called "superpower" cards.