Archon: The Light and the Dark was a game developed by Free Fall Associates which loosely modeled the game of Chess, with a number of additions to the gameplay. It was programmed by Anne Westfall, and released originally for Atari 8-bit computers in 1983. It was quickly ported to a number of different systems, and was well-received.
Each level of this abstract puzzler challenges the player to set up a network of pipes to allow an unspecified substance known as 'flooz' to flow through as many of those as possible. The pieces are offered in random order, and there are seven different types - straight lines going horizontally or vertically, corners rotating in each of the four directions, and cross-over pieces which carry the flooz straight across horizontally and vertically. Each of these can be entered from either side. When the flooz hits a gap, or a piece which the previous piece can't flow into, the pipe is finished.
Before the flooz starts flowing from its randomly-selected starting position, the player has several seconds to start placing pieces. They can be put down anywhere. However a situation that can often occur is there will be a long and complex piping arrangement set up, yet a gap somewhere remains to be filled. Players are able to replace a piece with another in the same square (to make it easier to flow the flooz that way), but for a slight scoring penalty.