Race your pawn to the far edge. On your turn, move one step or drop a wall to force your opponent the wrong way. Nobody can ever be fully sealed in.
You can play without a username, but no stats are saved for you that way. There's no password and no reset — remember your username exactly, since entering it again just logs you back in.
Closing the tab, navigating away, or forfeiting mid-game counts as a loss. So does going idle: if 2 minutes pass with no move on your turn, that's an automatic loss too.