Main loop: Main flight loop (Part 1 of 16)

       Name: Main flight loop (Part 1 of 16)                         [Show more]
       Type: Subroutine
   Category: Main loop
    Summary: Seed the random number generator
  Deep dive: Program flow of the main game loop
             Generating random numbers
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * DEATH calls via M%
             * Main game loop (Part 2 of 6) calls via M%
             * MVTRIBS calls via NOMVETR


 The main flight loop covers most of the flight-specific aspects of Elite. This
 section covers the following:

   * Seed the random number generator


 Other entry points:

   M%                   The entry point for the main flight loop

   NOMVETR              The re-entry point in the main game loop for when there
                        are no sprites to move


.M%

 LDA K%                 ; We want to seed the random number generator with a
                        ; pretty random number, so fetch the contents of K%,
                        ; which is the x_lo coordinate of the planet. This value
                        ; will be fairly unpredictable, so it's a pretty good
                        ; candidate

 STA RAND               ; Store the seed in the first byte of the four-byte
                        ; random number seed that's stored in RAND

 LDA TRIBCT             ; If TRIBCT is non-zero then we have some Trumbles in
 BEQ NOMVETR            ; the hold, so jump to MVTRIBS to move their sprites
 JMP MVTRIBS            ; around the screen, if applicable
                        ;
                        ; The MVTRIBS routine jumps back to NOMVETR when it has
                        ; finished moving Trumbles around

.NOMVETR