Exploring caves is fun in co-op; games like Spelunker HD Deluxe are proof of that. There's more than one way to delve a cave, though. Brave Cave from new indie developer Hit Start Studio is an upcoming puzzle platformer with a Chariot-like emphasis on co-op. It will support both local and online co-op for two players, so everybody will have a chance to cooperate their way through the brave and dangerous caves with a friend.
In Brave Cave, a human dude and his robotic companion must work their way through numerous rooms of a hazard-filled cave. The game (or at least its demo) MUST be played in co-op because single-player is not supported. Each character has a unique ability that can help the other player get past obstacles. The human guy has drop a rope down ledges for his companion to climb, and the robot can boost the jumps of his warm-blooded buddy. Additional powers will come into play in new areas, but those basic abilities can get the brave bros through a variety of obstacles. If either player dies in a room, the team must restart the room, so it's best to tackle the cave carefully.
After playing the Steam demo for a short while, I'm quite impressed with the game. The pixel art is well drawn and the level design makes good use of each character's abilities. There is some unattractive hand drawn artwork used as cover art and on the character select screen that I hope will be replaced in the final game, however. Also, the co-op focus here is great, but the game would find a larger audience if the developer added single-player support as well. Allowing a solo player to swap characters can't be that hard.
Brave Cave is due on Steam by the end of this year. In the meantime, be sure to check out the free Steam demo.