Resource centre for ZX Spectrum games
using Manic Miner and Jet Set Willy game engines
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Message: 6974
Author: ian.rushforth
Date: 12/12/2016
Subject: Re: JSWED 2.3.0: Andrew's comments (Chapters 1 to 5)
Andrew wrote:
> ghost-conveyors [are] conveyors which extend beyond the bottom-right [in cell-row 15], creating a mirage in cell-row 8...
... or alternatively, they can be created by conveyors which extend beyond the right-hand edge of the screen in cell-row 7, creating a mirage at the top-left of the screen (in cell-row 0)! In this case, a row of conveyor blocks will extend along the left-hand side of cell-row 8 - such blocks will act as a conveyor in terms of their effect on Willy, but they will be non-animated.
So effectively, the two aspects of the extension of the conveyor beyond the right-hand side of the screen - the mechanical and animation components, as it were - are separated by eight cell-rows on the left-hand side.
**
Incidentally, on the subject of quirky aspects of conveyors, I believe that in Manic Miner, if you attempt to create a cavern with a Conveyor Length Byte value of zero, then you will actually end up with a conveyor that is 256 cells in length! (The conveyor length is loaded into the B register and the conveyor is distributed via a DJNZ loop - B is decremented below zero in the first instance, before its value is checked.)
Thus the conveyor animation would either affect half of the cells in the playable area of the screen, or if the start coordinates of the conveyor haven't been defined, then the program may try to overwrite 256 bytes elsewhere in the code?
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