When you get stuck in a level, the boosters may help you get victory. You could just select to use one or more boosters by tapping them before PLAY.
The followings are boosters in our game:
UP: Bring the ship up a level.
MAX: upgrade the ship to the maximum for a while.
Life: Revive once after death.
Rocket: Bomb all aliens in the field.
Shield: Not get injured for 10 seconds.
Time: 60s bullet time.
The booster Shield/Bomb will not be used immediately as you bring it to the battle field. When your finger stops tapping the screen, the game will slow down to leave you the time to use the booster. Then after you tap the Shield/Bomb, it takes effect at once and the Shield will protect your ship from getting injured for 10 seconds.
When you lift your fingers, the booster TIME takes effect. It can slow down the game, so that you could have time to escape the attack.