Walkthrough Information

Destroy asteroids and rocks for bonus shields and weapons.
Get some speed in a direction, then reverse direction as you let out a mine to "throw" it into a group of enemies.
Conserve your shots for nice big groups.
During bonus levels, use the mini map to seek out as many power ups as possible.
When playing level 21, blow up all the rocks and there's a special bonus prize.
Once past level 5, each rock destroyed has a 5% chance of having the Star Clubber in it. However, each level can only have 1, so you can stop looking after you've found it.
The Star Clubber can destroy as many rocks as you want, but only so many enemies before it blows up!
When you have enemies on your tail, drop a mine and then slow down. The enemy will also slow down - this trick will keep them in the mine's blast radius.