It took really long after the first wave to spawn the 2nd wave, I actually thought the game might have crashed. Same for the 2nd and 3rd wave; I quit after that. The 'rewind' labels are in front of the one below them; it might have been clearer to just change the sprite color of the wind icon to indicate it needs to happen, and maybe add a button to call in the next wave; that way, players can choose their own pace and won't have to wait on an empty screen.