Hi, I didn't realize I had dms set to only users I follow, oops. There is a sound effect for when they merge, if it's not playing there might be something going on with the sound. If you leave the game open when you turn off the computer, the sound can sometimes stop working, but it should restart the audo if you just adjust the volume slider. As for particle effects, I have no current plans to add them, but if enough people want them it probably wouldn't be that hard.