Take care of the indicators you'll find below your ship panel. Some of them have a straight meaning.
You will see that it's tracked the number of enemies in the zone, as well as the number of goodies left and the number of bases to destroy. Then, there are the classic scoring spots, together with info about current wave and ships remaining.
The bonus counter gets decreased every second. Try to complete your wave quickly!
In the last row, you'll see icons displaying the current special equipment. You can activate the selected equipment using one of the 'Equip' keys; with the 'Choose' key, you can cycle thru all available equipment types (mines, smart bombs, teletransports). You'll gain equipment as you fetch green barrels. In the 'Bonuses' section you'll find some rules to keep in mind when looking for a goody. You'll definitely *need* some equipment to sustain the higher waves.