Liquid Kids (JP: Mizubaku Daibouken, or "Great Liquid Adventure") is a spin-off of Taito's classic Bubble Bobble. The player is Hipopo, a platypus (although he's said to be a hippo) who is trying to save his fellow hippos, as well as Tamasun - Hipopo's love interest - from the Fire Devil.
The game was originally released in the Arcade in 1990 in both Japan and North America. The game would then be ported to the PC Engine in 1992 by Taito themselves, where it remained a Japan-exclusive. This version of the game would later be added to the Wii's Virtual Console in 2008.
The game also saw a Saturn port in 1998, published by Ving. An Amiga port for PAL regions was developed by Ocean Software but never released, though the full disk image has been disseminated online. The game was also included in the compilation Taito Legends 2, released on PS2, original Xbox and PC in 2006.
Basic gameplay consists of jumping and throwing bubbles. Unlike Bub and Bob's bubbles, Hipopo's bubbles don't float up. In fact, they are filled with water and pop as soon as they hit something. After popping, water flows out and freezes any enemies it touches (enemies will appear out of fiery portals).
If Hipopo throws too rapidly, the bubbles will become small and ineffective until some time is given to recharge. The player can hold the throw button down to charge the bubble. Doing so will increase the size of the bubble, thus letting the water flow further than it would otherwise. Once an enemy is frozen, Hipopo must touch them to defeat them. The enemy is then kicked at a high speed, killing any enemies in the way. Wait too long and they regain consciousness and continue fighting. Most enemies are specific to the level, though there are a few that can be seen throughout.
Levels without bosses are won by freeing a hippo at the end of the level. Each world has three levels (or two if the right doors are chosen) and each world has a boss. At the end of every boss fight, the player has a choice of two doors. They both lead to the next world, but one brings Hipopo to the start, while the other brings him a little further in. Hipopo must make it through all the worlds to finally face off against the Fire Devil.
Throughout the game Hipopo will find items as well. They typically appear out of nowhere, though not all of them do. Items usually temporarily increase water power (so there's no need to charge), increase run speed, clear the screen of enemies, or just provide some points. Some of the items that can be found include roller skates, buckets of water, pig heads, lightning bolts and lots of food.