Replay Lost Rounds
If you lose a round, don't return to the main menu or pay to continue. Instead, close the app and then reopen it. You should find an option to continue from the Play menu. You'll resume play from the round you just lost, which gives you a chance to make any adjustments required to win (though all abilities will be in a cooldown state).
Infinite Monkey Money
Tap a chest to open it and obtain money, then close the chest and exit the app. Now access your device's Date and Time option, from the Settings menu. Set the time forward one day and open the app again. You should be able to open the chest for more money. You can repeat this procedure as often as you like, if you don't mind messing with your device's time.
Keep in mind this is a level based game where you will play consecutive levels and you will be able to unlock levels as you play.
Dart Monkeys will throw darts immediately once in range of Bloons.
Most Bloons can be taken out with just one dart but may require more monkeys when there’s a horde of them.
Long Range Darts will increase the range of the Dart Monkey dramatically.
If you watch the bottom of the screen at the end of each round, you will receive a nice hint about what may happen soon in the future.
Secret Agents are additional help you can hire to provide you with more firepower and defense mechanisms when you need them the most.