Resource centre for ZX Spectrum games
using Manic Miner and Jet Set Willy game engines
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Message: 6900
Author: ian.rushforth
Date: 05/08/2016
Subject: Re: Mirror MM/JSW / MM - JSW Conversions
Just to add that, from Andrew's comment (quoted in my previous message) it sounds as if the mirroring process does set Bit 7 of Byte 0 (initial swing direction), but does not set Bit 7 of Byte 1 (initial starting point of the Rope).
And there's no indication that the mirroring process does anything about the Segment Drawing Byte (Byte 5), i.e. switching the top of the Rope from occupying the left-hand side of its column, to the right-hand side, to give true symmetry.
Incidentally, I recently tried creating a 'Fat Rope' by filling in two consecutive pixels of the Segment Drawing Byte (i.e. inserting a value such as #C0 or #03 at #92B5). But as it approached the widest part of its swing, the segments became horizontally 'detached'! This is because, when the filled-in pixel of a particular segment is incremented past a cell-column boundary, the x-coordinate of the segment of Rope under consideration (stored in Byte 3 of the Rope Definition) is also incremented. But if two adjacent pixels are filled in then this incrementation is triggered twice in succession!
(N.B. The above description applies when the Rope is right-of-centre. When it is left-of-centre, replace all instances of the word 'increment' in the above with 'decrement'.)
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