5across is a passion project of ours. 5across uses the Socket io JavaScript library, enabling realtime, bi-directional communication between web clients and server, allowing players to work on puzzles together simultaneously, either cooperatively with friends or challenging each other, and also hosts an in-game chat system for talking through puzzles. The next beta release will extend support to mobile, as well as add in-game music and even team competitions and game ranking. But why read about it- check it out at www.5across.com.