Game is ok, but you spend 90% of the time watching ads. To start a round, you watch a 30 second ad, to end a round you watch a 30 second ad, to upgrade, you watch a ad, etc, etc. Each round of the game only takes about 15 seconds! I realize app companies need to make money somehow, but I will never give a positive rating to a game that is 90% watching ads! Unacceptable!