The Black Forest consists of a series of four Flash games, starring a black square with two white dots for eyes. Each game revolves around the same gameplay mechanic applied in drastically different fashion.
Your black square - or ghost, as the designer Pixelate credits him - can only move via the arrow keys. In the first game, he's trying to find his way out of a pitch dark maze. He finds help from the red ghosts who, once encountered, will highlight the path as they randomly patrol the maze. If further fleshed out, I could see this being developed into a neat little puzzle game.
Game 2, pictured, sees you piggybacking the jumping pink ghosts to reach the higher platforms and collect the diamonds.
Have a play with all four and let me know which one you like the most.