Author Topic: NES Infinite Vertical "Scroll"  (Read 3882 times)


  • Bob-Omg
« on: July 14, 2014, 08:05:06 PM »
Why in basically all NES games do characters or objects that go above or below the screen by half a block temporarily get separated in half and appear on the opposite side of the screen vertically?

Examples include:

- SMB where if a Mushroom falls off-screen, and you jump off-screen right above it, you obtain it, or you can stomp an enemy right as it starts going off-screen if you do the same jump above it.
- Excitebike (seen in a TAS), where if the rider goes too high (then eventually off-screen), he teleports in from the bottom of the screen.
- Cheetahmen (referencing the AVGN episode covering it), where when he does a jumping glitch and goes too far up the screen, he dies, but the death animation is split in half between the top and bottom.

It would seem to me that that is just the way the NES is since this occurs across a wide range of games. Though, it does seem to happen only in sidescrollers (or at least games that allow you TO go off-screen one way or another.
Formerly quite reasonable.

« Reply #1 on: July 14, 2014, 09:52:52 PM »
My guess would be a lot of NES-era games only check to see if the lower eight bits of objects' positions match up (within a tile's width or such); doing so would effectively treat two objects that were 256 pixels apart vertically as being in the same location.  In the case of Super Mario Bros., I believe most objects are 'killed' once they fall two rows of blocks beneath the screen (i.e. 256 pixels from the top), however, checking just the lower eight bits means you can cause a collision to register by jumping just above the top of the screen.
« Last Edit: July 14, 2014, 09:55:19 PM by jdaster64 »
If she is indeed genetically mutated such that she has an eye in the back of her head, then I guess that she is genetically mutated and has an eye in the back of her head.


  • Kansas
« Reply #2 on: July 15, 2014, 07:29:50 PM »
In Rainbow Islands, on the Goal In screen at the end of each stage, and at each boss fight, Bubby can reach the bottom o the screen by way of the top if he casts his rainbows high enough and jumps off of them properly.
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