Drawing pixels: ylookuph

       Name: ylookuph                                                [Show more]
       Type: Variable
   Category: Drawing pixels
    Summary: Lookup table for converting a pixel y-coordinate to the high byte
             of a screen address (within the 256-pixel-wide game screen)
    Context: See this variable in context in the source code
 References: This variable is used as follows:
             * CPIX2 uses ylookuph
             * HLOIN uses ylookuph
             * LOIN (Part 3 of 7) uses ylookuph
             * LOIN (Part 4 of 7) uses ylookuph
             * LOIN (Part 5 of 7) uses ylookuph
             * PIXEL uses ylookuph
             * TT66simp uses ylookuph


 The address returned is indented by four character blocks from the edge of the
 screen (that's the $20 part, as each character is 8 bytes, and 4 * 8 = $20).

 This is because the first four characters of every character line are blank,
 so the 256-pixel-wide game screen is centred in the Commodore 64's screen
 width of 320 pixels.


.ylookuph

 FOR I%, 0, 255

  EQUB HI(SCBASE + $20 + ((I% AND $F8) * 40))

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