Nintendo Gauntlet

I finally received Licensed Gauntlet for Nintendo today. And like most games I receive I try to disect what the programmers were thinking when they make a game. Gauntlet for Nintendo is unique. Anyone who has played it knows the screen can fill up with enemies really fast. And when I say fill I seriously mean fill! On some stages it seems there is an enemy in every space of the screen!

This got me to thinking... why isn't there crazy amounts of slow down in this game? You consider a game like Super Mario Bros. or Bubble Bobble and if you have more than three or four enemies on the screen you'll either suffer crazy slow down or flicker.

I know why this happens in those games... with more enemies on the screen the Nintendo has to draw more sprites. The system can slow down or the sprites can be drawn less frequently (causing flicker) to keep the game moving. both of those options suck.

So why is it that Gauntlet can have a screen full of enemies and no slow down and no flicker? The answer is pretty unique. Now before I go explaining it I may have my terminology wrong, and if I do feel free to correct me in the comments.

The enemies in Nintendo Gauntlet are not sprites. Instead, they are part of the background! Huh? Consider Super Mario Bros. for a moment. Mario and the enemies move around on the screen on top of a static background that does not change. For each frame of animation the Nintendo draws the curent background and then the enemies and Mario are drawn on top of it. Once the picture is finished it is then displayed on the screen. I believe its called a "frame buffer". If the Nintendo didn't do this our eyes would literally see the sprites get drawn on the screen and the background drawn on top then the sprite drawn on top and repeating over and over and over (I believe this is referred to as "tearing"). The frame buffer prevents this but the system is still limited in the number of sprites it can draw before slow down and flickering occur.

Since the background is drawn once for each frame of animation the programmers were smart enough to make the enemies drawn as part of the background. This would mean that there would never be slow down or flicker associated with it no matter how many enemies are on the screen. Whether it was drawing a ghost or just a floor tile it would take the NES the same amount of time to draw it.

When watching the game this makes perfect sense. The enemies do not move smoothly. Instead they move around in a kind of choppy fashion. The backround is composed of "tiles" and they each have a fixed position. The enemies move in all directions at the same distance of the width of the fixed title.  So instead of drawing a sprite for each of the enemies, the programmers are having the background tiles drawn to look like the ghosts, orcs, etc.

There is one exception to this rule: Death.  Death moves smoothly like your avatar does.  So Death is a sprite and not a background.

I wouldn't be surprised if other games used this same technique.  Late in the life of the NES there were some incredible games that seemingly did not have slow down or flicker, and its quite possible this technique is what over came the hardware limitations.