Forums  /  Metroid series  /  Metroid (NES)  /  Enemy's slots MAP and some explanation

Back in the days i made this map that shows enemy's slots.

The whole game are made out of "screens". When scrolling cross border of one of those screens then game tries to spawn enemies on that screen. Enemies spawn only in particular ram slots. If that slot occupied by enemy or pick up then enemy wouldn't spawn even if all other ram slots are available. Also when enemy spawn in particular slot it tries to move in the same direction as previous enemy in the same slot.
For example i have troubles with that crawling guy near energy tank. If he moves to the left he blocks the way when i try to go back after E-tank and that could cost me a lot of time. So just by watching at map i know that he spawns in slot 2. And previous enemy that was spawn in that slot was that jumping guy on the ceiling. So by killing jumpin guy while he moves to right i can make so crawling guy near the energy thank will also move to the right.

So if you have troubles like that in the runs you can try use that map to manipulate enemies. Just find in what slot problematic enemy spawns and what was previous enemy in that slot. So you can try to kill previous enemy in certain way to make other enemy move to different direction. Or you can try to keep previous enemy alive, so when scrolling cross the screen with problematic enemy it wouldn't spawn. By using this map you can know exactly whats going on and there is no need to guess what to do or something like that

edit: also those small fly-like enemies works differently. You can't manipulate or despawn them

AngrylanksAngrylanks, AceEbbAceEbb and 4 others like this. 

Haven't had a chance to read this until now... this is fantastic! Thanks so much for sharing this information, Koh.... and for the hard work you put into the complete map of enemy index #'s. All sorts of enemy manipulations are now in our grasp. Very eager to play around with this.


This is amazing. Moving a link to resources.

Also, I'm assuming cheeros just take a random spot? Cos the first metroid in the "cheerio room" sometimes doesn't spawn, which i assume is because a cheerio is occupying its memory spot.

AceEbbAceEbb and WolfMerrikWolfMerrik like this. 

Rinkas uses same RAM slots as enemies, but their spawn was looking to random to me so i didn't mark them. But yes, they can prevent spawn of Metroids.

Also it's cool and all, but it's really hard to find places where this could be useful. Usually it takes more time to turn around enemies than you can save by turning them around ;C At least this is true for 100% category. Maybe it can be useful for different categories.


Its super helpful. While most routes seem pretty optimized, this makes it easier to explore other options, but more importantly this makes it SUPER easy to figure out why you're getting a bad pattern (for instance ball pattern). Super simple and helpful.


This was discussed on McFly's stream. Here is my thoughts about cloud room.

Again, rooms are made of separate screens. I roughly marked boarders of those screens on picture above. So when scrolling (camera) position are exactly at the middle of one of those screens... I don't know how better explain it. Like borders of camera lines up with borders of one of those screens then enemies for some reason can bounce of the edge of the screen. It's better to watch this video:

It should be pixel perfect scrolling (camera) position. If you just scroll 1 pixel to the side then enemy stop bouncing of the edge of the screen.

Also when you jump you have slower horizontal speed that when you walk. So when you go trough that room it's possible to exactly line up that enemy and scrolling position so enemy turns around. It depends on how much your jump. That's why that green dude can get in your way sometimes. Because one of green dudes turns around by bouncing of the edge of the screen. It can be unnoticeable, but next green dude now are in your way.

This is only assumption. Sorry for bad English