We're working on a major update that will soon add support for online multiplayer - and a new map, too!
Online multiplayer will be accessible via the usual new game screen for the player who hosts a game, and once the host has set up a server, the other player joins by pressing a new button (with a globe icon) in the main menu, to see the list of servers available to join. The game auto-generates a random server name that the second player can look for, in order to join the correct server.