.FLIPName: FLIP Type: Subroutine Category: Stardust Summary: Reflect the stardust particles in the screen diagonal
Swap the x- and y-coordinates of all the stardust particles and draw the new set of particles. Called by LOOK1 when we switch views. This is a quick way of making the stardust field in the new view feel different without having to generate a whole new field. If you look carefully at the stardust field when you switch views, you can just about see that the new field is a reflection of the previous field in the screen diagonal, i.e. in the line from bottom left to top right. This is the line where x = y when the origin is in the middle of the screen, and positive x and y are right and up, which is the coordinate system we use for stardust).
This variation is blank in the Disc (flight), Disc (docked), 6502 Second Processor, Master and Electron versions.
Cassette\LDA MJ \ These instructions are commented out in the original \BNE FLIP-1 \ source. They would have the effect of not swapping the \ stardust if we had mis-jumped into witchspace
This variation is blank in the Cassette, Disc (flight), Disc (docked), 6502 Second Processor and Electron versions.
MasterLDA #DUST \ Switch to stripe 3-2-3-2, which is cyan/red in the STA COL \ space view
The Electron version only shows 10 stardust particles at once, compared to 20 in the Master version or 18 in the other versions.
Tap on a version to expand it, and tap it again to show to all variations.
Cassette, Flight, Docked, 6502SP, Master
ElectronLDY NOSTM \ Set Y to the current number of stardust particles, so \ we can use it as a counter through all the stardustLDY #NOST \ Set Y to the number of stardust particles, so we can \ use it as a counter through all the stardust
.FLL1 LDX SY,Y \ Copy the Y-th particle's y-coordinate from SY+Y into X LDA SX,Y \ Copy the Y-th particle's x-coordinate from SX+Y into STA Y1 \ both Y1 and the particle's y-coordinate STA SY,Y TXA \ Copy the Y-th particle's original y-coordinate into STA X1 \ both X1 and the particle's x-coordinate, so the x- and STA SX,Y \ y-coordinates are now swapped and (X1, Y1) contains \ the particle's new coordinates LDA SZ,Y \ Fetch the Y-th particle's distance from SZ+Y into ZZ STA ZZ JSR PIXEL2 \ Draw a stardust particle at (X1,Y1) with distance ZZ DEY \ Decrement the counter to point to the next particle of \ stardust BNE FLL1 \ Loop back to FLL1 until we have moved all the stardust \ particles RTS \ Return from the subroutine