Universe: SOLAR

       Name: SOLAR                                                   [Show more]
       Type: Subroutine
   Category: Universe
    Summary: Set up various aspects of arriving in a new system
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * TT18 calls SOLAR


 Halve our legal status, update the missile indicators, and set up data blocks
 and slots for the planet and sun.


.SOLAR

                        \ --- Mod: Code removed for Elite-A: ------------------>

\ LSR FIST              \ Halve our legal status in FIST, making us less bad,
\                       \ and moving bit 0 into the C flag (so every time we
\                       \ arrive in a new system, our legal status improves a
\                       \ bit)

                        \ --- And replaced by: -------------------------------->

                        \ We now want to extract bits 3-10 of QQ8(1 0) into A,
                        \ so we can subtract this value from our legal status in
                        \ FIST (so the further we travel, the quicker our legal
                        \ status drops back down to clean, as we put more
                        \ distance between us and our crimes - specifically, we
                        \ drop 1.2 FIST points for each light year, as we
                        \ subtract (QQ8 / 8) from FIST, and QQ8 contains the
                        \ distance in light years * 10)

 LDA QQ8                \ Set A to the low byte of the distance to the selected
                        \ system in QQ8(1 0), so (QQ8+1 A) contains the distance

 LDY #3                 \ We're going to extract bits 3-10 by shifting QQ8(1 0)
                        \ right by 3 places, so we start by setting a loop
                        \ counter in Y

.legal_div

 LSR QQ8+1              \ Shift (QQ8+1 A) to the right by one place
 ROR A

 DEY                    \ Decrement the loop counter

 BNE legal_div          \ Loop back until we have shifted right by 3 places, by
                        \ which point A will contain bits 3-10 of QQ8(1 0)

                        \ We now subtract A from FIST, and subtract 1 more,
                        \ making sure we don't reduce FIST beyond 0, which we do
                        \ by doing the subtraction in reverse and then negating
                        \ the result with one's complement

 SEC                    \ Set A = A - FIST (which we will negate later)
 SBC FIST

 BCC legal_over         \ If the subtraction underflowed, i.e. A < FIST, skip
                        \ the following instruction

 LDA #&FF               \ A > FIST, so we set A = &FF so the EOR flips this to
                        \ 0, so FIST gets set to 0 when we travel far enough to
                        \ clear our name

.legal_over

 EOR #&FF               \ Flip all the bits in A to negate the result, so if the
                        \ subtraction underflowed, i.e. A < FIST, we now have
                        \ A = FIST - A - 1

 STA FIST               \ Update the value of FIST to the new value in A

                        \ --- End of replacement ------------------------------>

 JSR ZINF               \ Call ZINF to reset the INWK ship workspace, which
                        \ doesn't affect the C flag

 LDA QQ15+1             \ Fetch s0_hi

 AND #%00000011         \ Extract bits 0-1 (which also help to determine the
                        \ economy), which will be between 0 and 3

 ADC #3                 \ Add 3 + C, to get a result between 3 and 7, clearing
                        \ the C flag in the process

 STA INWK+8             \ Store the result in z_sign in byte #6

 ROR A                  \ Halve A, rotating in the C flag (which is clear) and
 STA INWK+2             \ store in both x_sign and y_sign, moving the planet to
 STA INWK+5             \ the upper right

 JSR SOS1               \ Call SOS1 to set up the planet's data block and add it
                        \ to FRIN, where it will get put in the first slot as
                        \ it's the first one to be added to our local bubble of
                        \ this new system's universe

 LDA QQ15+3             \ Fetch s1_hi, extract bits 0-2, set bits 0 and 7 and
 AND #%00000111         \ store in z_sign, so the sun is behind us at a distance
 ORA #%10000001         \ of 1 to 7
 STA INWK+8

 LDA QQ15+5             \ Fetch s2_hi, extract bits 0-1 and store in x_sign and
 AND #%00000011         \ y_sign, so the sun is either dead centre in our rear
 STA INWK+2             \ laser crosshairs, or off to the top left by a distance
 STA INWK+1             \ of 1 or 2 when we look out the back

 LDA #0                 \ Set the pitch and roll counters to 0 (no rotation)
 STA INWK+29
 STA INWK+30

 LDA #129               \ Set A = 129, the ship type for the sun

 JSR NWSHP              \ Call NWSHP to set up the sun's data block and add it
                        \ to FRIN, where it will get put in the second slot as
                        \ it's the second one to be added to our local bubble
                        \ of this new system's universe