GreenDayRlz, on Sun Dec 12, 2010 10:17 PM, said:
I noticed you called them players, and then mentioned missiles, are they different?
Yeah, the 2600 doesn't use the same concept of sprites as the NES. There are only a few objects available to draw stuff: 2 players, 2 missiles, 1 ball and the playfield. They were probably named like this because of the simplistic games the designers of the video chip had in mind. Also unlike the NES, the 2600 doesn't have enough video memory to hold the picture of an entire frame, only a handful of registers that define how a single scanline will look. If programs don't change the registers every scanline, they'll look the same all the way from the top of the screen to the bottom. There are also only 4 "active" colors at any given time: one for player 0 and its missile, one for player 1 and its missile, one for the playfield and the ball, and one for the background.
The background color is like color 0 on the NES, it fills the entire background and the other objects are drawn on top of it. The playfield is 40 "blocks" wide, but there are only 20 bits for storing its pattern, so the right side of the screen is either a mirror or a copy of the right side. Alternatively, the program can overwrite the 20-bit pattern mid-scanline to make the halves unique. The players are 8 pixels wide, but they can be stretched to twice or 4 times their regular width. They can also have 2 or 3 copies (i.e. the same player shows up multiple times on the same scanline) when they are not stretched, but there are only a few hardwired options for the spacing between copies. The missiles and the ball are only 1 pixel wide (so they are either "on" or "off" on any given scanline), but they can be stretched to 2, 4 or 8 times that.
As you have probably already seen, a lot of games are very creative with the use of these objects. A missile doesn't necessarily have to be used as a projectile, and a ball doesn't have to be kicked or thrown around. In "3d" racing games like Enduro or Pole Position for example, they are used to draw the sides of the road. The steps of the escalators in Keystone Kapers are drawn with the ball. By changing the colors, positions and patterns every scanline, games are able to build very complex scenes out of these few objects.