Across the Obelisk
Turn Indicator
I would like to suggest implementing an optional turn indicator in Multiplayer.

When playing Obelisk with friends it is easy to miss when it is your turn. I find myself telling people that I play with that it is their turn quite frequently. I believe a notification sound, such as those found in CIV 5 or other multiplayer turn-based games, would be helpful. Ideally this ring, ping, or whatever noise is chosen, should be short and clearly identifiable against the other game sounds.

As this option may not be for everyone, including it in the lobby or host settings would enable people to choose to use this feature.