Shooting is automatic, but you must manage the size and status of your fleet.
On the right side of the screen there are buttons to use power ups like bombs, freezing enemies and a defense shield. Generally if you manage your fleet well you should not need these until you are deep into a game. Generally if a level starts poorly it is best to use these power ups early in the level rather than later into the level.
Bombs: Allows you to blow up the enemies near a particular portion of the screen.
Freeze: Causes the enemies to pause without shooting for a period of time.
Mines: Allows you to set mines on the screen where enemies will blow up if they hit them. The first click pulls up a grid and the second click allows you to set the blue mines.
Defense: makes your characters harder to hit.
As you collect coins spend them to add more ships to your fleet. Each time you buy a ship in any given class it gets more expensive. The shopping cart is in the lower right corner of the game.
If a ship runs out of power it does not die, but rather goes to the base for repairs – provided the base has an open space for it to be repaired. If the base does not have any open spaces then the ship does die!
If your ships are nearly out of power you can put them in the base for repairs. Click on a ship to bring it back to the base.
When ships are full power they do not automatically return to the playing field, so you have to click on them and drag them out to bring them back into the game.
You should always keep at least one base slot open at all times so you can get presents, which typically contain ships though may contain other power ups.
You can merge two ships together to create a more powerful ship. Drag one ship onto the next to merge them.
If you have too many ships on the screen to make sense of then it helps to keep merging them into more powerful ships at the base.
You start the game with 5 hearts and each time aliens cross the line you lose one of the 5 hearts. When you have less than 5 hearts some of the presents you are given in the game will be more hearts.
This game has well over 100 levels. There is a pause button in the upper right corner of the game.