Fireboy and Watergirl

Fireboy and Watergirl is the quintessential cooperative browser puzzle platformer. One player controls Fireboy — immune to fire, instantly killed by water — and the other controls Watergirl — immune to water, instantly killed by fire. Both must navigate each level simultaneously, reach their respective colored exits, and help each other past obstacles neither can handle alone.

The puzzle design is built around this elemental asymmetry. Fireboy can walk through lava rivers Watergirl must leap over. Watergirl can pass through water channels Fireboy cannot touch. Pressure plates, levers, and switches require one character to activate while the other crosses a simultaneous hazard. Neither character can finish a level without the other.

Five forest temples have been released, each with increasing complexity and new mechanics. The Forest Temple is the classic starting point. The Ice Temple adds sliding on ice surfaces. The Fire Temple and Water Temple push the elemental mechanics to their limits. The Crystal Temple introduces mirrored movement puzzles.

Uniquely, Fireboy and Watergirl can also be played solo — one player controls both characters with two hands (WASD for one, arrows for the other). Solo play requires coordinating two characters simultaneously, which is genuinely challenging and a different experience from two-player cooperative.