We really liked the digital adaptation of the famous board game Splendor [$6.99] when it originally came out, although we did note the lack of online multiplayer as a factor that took away some of the port's shine. That is not an issue anymore, though, since the latest update has finally added online multiplayer, and it comes with plenty of features. The online multiplayer part is cross-platform (you'll need a Days of Wonder account to log in and play) and includes both ranked and unranked games from 2-4 players. You can even make private games by adding a password to your game.
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Splendor also has a Karma system, which is the developer's way to discourage people leaving midway through the game. If you drop out of a game, you lose Karma, and that matters because when you create a multiplayer game, you can choose to only accept players over a specific Karma threshold. Cool idea and not one you usually see in digital ports of board games. The update is live now, so go play online.