Demo: TWIST

       Name: TWIST                                                   [Show more]
       Type: Subroutine
   Category: Demo
    Summary: Pitch the current ship by a small angle in a positive direction
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * DEMON calls TWIST
             * DEMON calls via TWIST2


 Other entry points:

   TWIST2               Pitch in the direction given in A


.TWIST2

 EQUB &2C               \ Skip the next instruction by turning it into
                        \ &2C &A9 &00, or BIT &00A9, which does nothing apart
                        \ from affect the flags

.TWIST

 LDA #0                 \ Set A = 0

 STA RAT2               \ Set the pitch direction in RAT2 to A

 LDX #15                \ Rotate (roofv_x, nosev_x) by a small angle (pitch)
 LDY #9                 \ in the direction given in RAT2
 JSR MVS5

 LDX #17                \ Rotate (roofv_y, nosev_y) by a small angle (pitch)
 LDY #11                \ in the direction given in RAT2
 JSR MVS5

 LDX #19                \ Rotate (roofv_z, nosev_z) by a small angle (pitch)
 LDY #13                \ in the direction given in RAT2 and return from the
 JMP MVS5               \ subroutine using a tail call