Fireboy must avoid the water and Watergirl must avoid the fire, and be careful, the green mud kills them both! You can collect diamonds for extra points!

You navigate characters Fireboy and Watergirl - either alone or with a friend - through various puzzles. Fireboy can walk in lava, but not in water. Watergirl can walk in water, but not in lava.

Fireboy and Watergirl was the ultimate multiplayer game. Long before controllers and consoles were more prominent, multiplayer games were more challenging to pull off.

Fireboy and Watergirl 1: Forest Temple has that early internet, Flash game sauce. Each level has a series of elemental puzzles that grow increasingly complex.

That seems to have become the unexpected key driver for the popularity of the Fireboy & Watergirl franchise. As both single and a two-person game; the dual-play aspect has driven its success.