The no-fire cheat in Galaga is well known. This video shows that we can actually 'partially' cheat by reducing the number of bullets the enemies shoot to only 1 bullet on the screen at a time. In fact, we could reduce the number of bullets on the screen from 8 down to any number less than 8.
First an explanation of the no-fire cheat:
* Galaga keeps track of enemy shots using an array of 8 slots.
* There can be up to 8 enemy shots on the screen at once, and each time an enemy shot is fired, that shot fills one of the 8 slots in the array. When an enemy attacks, it checks to see if there are open slots. If there are, that means there are shots available. If all 8 slots are full, the enemy assumes there are already 8 shots on the screen and thus does not shoot.
* When a bullet reaches the bottom of the screen, that slot is cleared from the array, allowing for another shot to be fired in its place.
* Occasionally, an enemy will fire a bullet exactly on the left edge of the screen (at position x=0). These don't display on the screen but they fill one of the 8 slots. However, these bullets never get removed from the array, thus resulting in a 'clogged' slot.
* On average, a slot gets clogged every 2-3 minutes. If we wait long enough all the slots are clogged, resulting in the enemies thinking the screen is always already filled with 8 bullets and thus the enemies don't fire.
* While not shown in this video, this can be done on any stage in which enemies are firing. Most people assume it must be Stage 1 or Stage 2, which is incorrect. I streamed another video that shows this being done on other stages.
"Partially" cheating:
By stopping the no-fire cheat before it's completed, we can reduce the number of bullets from 8 to something less than 8. In this example, we reduce it to 1 bullet to make it obvious. If we reduced it only to 6 or 7 bullets, it would be less obvious, especially under a good player that quickly clears enemies.
Credit:
* I learned of this years ago from an analysis done by Christoper Cantrell. His work can be read here: [ Ссылка ]
* The video comes from a game I streamed from Pincadia during Gala-Gala.
