On the equipment screen select the white bug ship and put it on the grid area. Then choose the orange laser and drag it to the face of the shop keeper. Keep clicking the 'LEFT MOUSE BUTTON' until you get $500,000. You should now also be able to press the 'Esc' key to take you to the next level.
Insert the disk, and hold both mousebuttons until the title screen appears. When youre in the shop hold down 'HELP' and 'DEL' for a few seconds, now choose your ships as normal, but you have infinite energy.
To get more cash at the beginning of the game, select the smallest ship (the one at the top), then the weediest laser (the orange one with single beam), and place it on the shopkeepers nose. Hit the 'fire button' to get the cash boost!
When you are confronted by the first end of level guardian shoot off the bottom hooter (the one closest to the skull) then position yourself so that you are not shooting the last hooter (the top one). Make sure you are only shooting the bubbles that he fires at you. This should give you approximately 20 credits per second. This takes ages, but if you are persistent leave your room for an hour and come back.
In actual fact you can have twelve different ships. All you do is press 'F1' for the first ship fully decked with weapons. Pressing 'F2' for the second ship and so on. After a while you won't get any more ships because you will run out of money.
The best ship that will last the longest is the last one with the bottom three way laser, two non-moving satellites placed either side of the ship. Then get the arc satellite, sprite bomb and bouncing bombs. It is also very advisable in the later levels to get the shield.
Choose any of the 4 ships in the shop. Click the ship as usual onto the blue print screen and then choose the invincible icon (the one below the laser - the one to the right of the orange spiked ball). Now drag this icon to your ship and click it on and off the ship. Your money increases by 500 units. Drag the icon to the Alien Trash Can and trash it. Carry on doing this to boost your money to your heart's content.