How do I control the sound volume?

From the PLAY SCREEN:
1) Select SETTINGS from the main menu.
2) Adjust the SOUNDS slider to your preference (0% will effectively mute all sounds)

From the GAMEBOARD:
1) Tap the GAMEBOARD MENU button in the lower-right
2) Tap the SETTINGS BUTTON (gear icon)
3) Adjust the SOUNDS slider to your preference (0% will effectively mute all sounds)