Attacks
The St. Anger basic attack immediately damages enemies. Its effectiveness depends only on how fast you can tap. If other abilities are available, use them first. Keep all your abilities on cooldown but do not hesitate to use special abilities. Keep one big damage ability on backup just in case (for example, God Hammer). At about level 4, armored vehicles such as tanks and helicopters will begin to appear. Target them first. If they survive, they will do heavy damage. They are immune to elemental damage such as fire and lightning. Use physical damage from regular attacks to take them out.
Coins
You can collect a free gift every few minutes. The prize is coins that can be spent to upgrade your abilities. At the end of a level, you have a choice to watch a video advertisement to double your coins.
Merging
Basic creatures do not have special abilities. However after merging them into an advanced form, they will gain a random ability. Merging requires mushrooms, which are sometimes given after completing a level. If you merge two creatures and end up with an ability that is not useful, you can re-roll the ability by watching a video advertisement.
Police car
One enemy that will appear is a police car. Although it does not attack, when it is damaged it will activate its sirens, which cause other nearby enemies to increase their attacks. When you see a police car with a red aura, its sirens are active and you should try to take it out immediately.