Cursors.io

Cursors.io is a multiplayer maze game that emphasises co-operation and challenges players to contribute to the success of the online group. You guide your mouse cursor around the playzone looking for the exit, but there may be obstacles that need other players help, like pads that need X number of players to open the door. When you stand on the pad you may be opening the door for other players, but you also hope that others will stand on the pad to open the door for you as well.

Cursors.io is cited as the first of the very popular .io series of browser multiplayer games.