You'd think that FireBoy and WaterGirl would have a hard time getting along. After all, if they go too close, they could transform into a puff of smoke or a wisp of steam, respectively.

They can't exist without one other in FireBoy and WaterGirl: The Hidden Forest, though, because each stage is an ingeniously created puzzle that can only be solved by two characters working together.

The game finds you attempting to direct each character to their own unique exit by pulling levers, activating devices, and basically navigating your way through a series of Rube Goldberg-style puzzles in the latest installment of the popular FireBoy and WaterGirl series.

The key is that certain components can only interact with one of the characters. WaterGirl can only interact with blue objects, whereas FireBoy can only engage with red objects. Similarly, the former is incapable of surviving in water, while the latter is incapable of surviving in fire.

There's also material that kills both characters, as well as buttons and levers that can be used by either of them.

Usually, this entails WaterGirl taking one path while FireBoy goes another, or one of them standing on a pressure pad to allow the other through a doorway.

However, there are times when you'll need to figure out how to bring FireBoy and WaterGirl to the proper places in the right order to finish the level, such as by changing weights or pressing down pressure pads.

The premise of solving puzzle stages with several characters dates back to the 1990s' The Lost Vikings, but here's the twist: you may control both FireBoy and WaterGirl at the same time.

You can navigate WaterGirl and FireBoy through the stages at the same time by using WASD for WaterGirl and the cursor keys for FireBoy, which is as difficult as it sounds. You can always move one character at a time if you find this head-patting-tummy-rubbing workout too challenging.

Better yet, you may play the game with a friend, slumped over the same keyboard in the best tradition of multi-screen multiplayer action.

Here's where you can find FireBoy and WaterGirl: The Hidden Forest. There are also a lot of 2-player games on the Fireboy and Watergirl website.