is a popular series of online cooperative puzzle-platform games created by Oslo Albet. This game series stands out for its unique two-player mechanics, where players control two characters with contrasting abilities to solve puzzles and navigate levels.

Characters and Mechanics
In Fireboy and Watergirl, each player takes on the role of either:

Fireboy: immune to fire but vulnerable to water.
Watergirl: immune to water but vulnerable to fire.
The two characters have opposite attributes and must rely on each other’s abilities to avoid dangers, overcome obstacles, and reach the exit. Each level often has pools of fire and water, which one character can pass through while the other cannot. Additionally, there are obstacles like green goo that are deadly to both characters.

Gameplay and Objectives
The main objective is for both characters to reach their respective exits in each level, collecting gems along the way and navigating a series of platform-based puzzles. This requires players to carefully coordinate their movements, as certain puzzles require specific timing or cooperation to progress.

The levels are full of traps, levers, buttons, and platforms that the players must use to their advantage:

Levers and buttons open doors or move platforms.
Crystals are often scattered around and serve as collectible items.
Mirrors and beams of light add a new layer of puzzle-solving in certain levels, where players must manipulate light to progress.
Game Series and Levels
The Fireboy and Watergirl series has multiple installments, each introducing new mechanics and themed environments:

Fireboy and Watergirl in the Forest Temple: The original game set in a mystical temple with basic puzzles.
Fireboy and Watergirl in the Light Temple: Adds light-based puzzles where players reflect and refract light beams.
Fireboy and Watergirl in the Ice Temple: Introduces slippery surfaces and ice blocks, making navigation and timing more challenging.
Fireboy and Watergirl in the Crystal Temple: Features teleportation crystals, allowing players to warp to different parts of the level.
Fireboy and Watergirl in the Elements: Combines elements from all previous games, with levels themed around different natural elements.
Multiplayer and Single-Player Options
While traditionally played as a two-player game, Fireboy and Watergirl can also be played solo, where one player controls both characters using different keys. However, the game’s design is best suited to cooperative play, allowing two players to split responsibilities and solve puzzles together.

Popularity and Appeal
The game’s popularity stems from its cooperative, non-violent gameplay, which requires teamwork, problem-solving, and timing. It’s accessible for all ages, making it a popular choice for casual players, siblings, and friends looking for a fun and interactive puzzle game.

Summary
Fireboy and Watergirl is an engaging puzzle-platformer that promotes teamwork and coordination. With its variety of elemental-themed levels, cooperative gameplay mechanics, and ever-evolving challenges, it remains a favorite among online multiplayer games and a classic in browser gaming.