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⌂ ∞ ▽ The Sentinel on the BBC Micro

Cracker protection: SetCrackerSeed

       Name: SetCrackerSeed                                          [Show more]
       Type: Subroutine
   Category: Cracker protection
    Summary: Set up anti-cracker tile-related data that can be checked in the
             CheckCrackerSeed routine

    Context: See this subroutine in context in the source code
 References: No direct references to this subroutine in this source file




.SetCrackerSeed

 LDA stripData+78-32,X  \ Copy the contents of stripData+78 into the operand of
 STA CrackerSeed+1-32,X \ the unused LDA #0 instruction at CrackerSeed (this
                        \ location is presumably disguised as an instruction to
                        \ obfuscate this process)
                        \
                        \ At this point stripData+78 contains the third seed
                        \ number to be generated at the start of the
                        \ GenerateLandscape routine, where 81 seed numbers are
                        \ generated and stored at stripData
                        \
                        \ This third seed contains the high byte of the BCD
                        \ landscape number
                        \
                        \ This is because the seed generator is initialised
                        \ using the landscape number, and the third number out
                        \ of the shift register is unchanged and still contains
                        \ the initial value of that byte - see the
                        \ InitialiseSeeds routine for more details)
                        \
                        \ This value is altered in the AlterCrackerSeed routine
                        \ that runs as part of the gameplay routines, and is
                        \ checked in the CheckCrackerSeed routine that runs as
                        \ part of the SpawnCharacter3D routine when drawing the
                        \ landscape's secret code

                        \ Fall through into part 4 of SmoothTileCorners to
                        \ continue with the smoothing process