unregistered wrote:Are the background tiles able to be collision detected?
Not by hardware... but then again, neither are the sprites. Unlike the Atari 2600 for example, the NES doesn't have any sort of hardware features for collision detection (the sprite 0 hit is not meant for testing object collisions, it's meant for detecting the position of the beam for raster effects). All collisions between objects, no matter if sprite or background, are done in software, through comparisons of their coordinates in the game world.
Status bar would only be 8 pixels high
Remember that some of the image is cropped by the television, so you shouldn't have important information too close to the screen edges. So even if your information only needs 1 row of tiles to be displayed, it should be 1 or 2 rows away from the edge of the picture.
and would have one or two text stats, maybe it could be clear and at the top of the screen, like in Mario (is that a status bar?).
Yes, it's a status bar. It's not clear though, it just appears to be that way because it uses the same color as the sky for its background. There never is any background going behind it, because the status bar itself is drawn with background tiles, and the NES has only 1 background layer.
If you have little information to display, you could use sprites to display the status, like in Mega Man or Sonic The Hedgehog (not NES, I know, but it's a good example). It's simpler that way, because you don't have to worry about splitting the background, something that can be particularly hard if you are scrolling vertically. The disadvantage of using sprites is that since you can only show 8 of them side by side, you can't have a lot of information laid out horizontally (hence why Mega Man's energy bar is vertical).
We would like our levels to be 4 screens tall. "It's our first game, we're just experimenting." Thank you for your help!
Then SMB3's solution is not very good for you. You can use either vertical or horizontal mirroring (it depends on whether you prefer to have scrolling artifacts at the top and bottom or left and right of the screen - notice how SMB3 has some color issues at the right side because it uses horizontal mirroring) if you decide to display the status with sprites, and single-screen mirroring (one name table for the gameplay and the other for the status bar) if you stick to a background status bar.