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⌂ ∞ ▽ Elite on the BBC Micro and NES

Tactics: TACTICS (Part 4 of 7)

[Acorn Electron version]

       Name: TACTICS (Part 4 of 7)                                   [Show more]
       Type: Subroutine
   Category: Tactics
    Summary: Apply tactics: Check energy levels, maybe launch escape pod if low
  Deep dive: Program flow of the tactics routine

    Context: See this subroutine in context in the source code
 Variations: See code variations for this subroutine in the different versions
 References: No direct references to this subroutine in this source file




 This section works out what kind of condition the ship is in. Specifically:

   * Rarely (2.5% chance) roll the ship by a noticeable amount

   * If the ship has at least half its energy banks full, jump to part 6 to
     consider firing the lasers

   * If the ship is not into the last 1/8th of its energy, jump to part 5 to
     consider firing a missile

   * If the ship is into the last 1/8th of its energy, then rarely (10% chance)
     the ship launches an escape pod and is left drifting in space



 LDA TYPE               \ If this is not a missile, skip the following
 CMP #MSL               \ instruction
 BNE P%+5

 JMP TA20               \ This is a missile, so jump down to TA20 to get
                        \ straight into some aggressive manoeuvring

 JSR DORND              \ Set A and X to random numbers

 CMP #250               \ If A < 250 (97.5% chance), jump down to TA7 to skip
 BCC TA7                \ the following

 JSR DORND              \ Set A and X to random numbers

 ORA #104               \ Bump A up to at least 104 and store in the roll
 STA INWK+29            \ counter, to gives the ship a noticeable roll

.TA7

 LDY #14                \ Set A = the ship's maximum energy / 2
 LDA (XX0),Y
 LSR A

 CMP INWK+35            \ If the ship's current energy in byte #35 > A, i.e. the
 BCC TA3                \ ship has at least half of its energy banks charged,
                        \ jump down to TA3

 LSR A                  \ If the ship's current energy in byte #35 > A / 4, i.e.
 LSR A                  \ the ship is not into the last 1/8th of its energy,
 CMP INWK+35            \ jump down to ta3 to consider firing a missile
 BCC ta3

 JSR DORND              \ Set A and X to random numbers

 CMP #230               \ If A < 230 (90% chance), jump down to ta3 to consider
 BCC ta3                \ firing a missile

                        \ By this point, the ship has run out of both energy and
                        \ luck, so it's time to bail

 LDA #0                 \ Set the AI flag to 0 to disable AI, hostility and
 STA INWK+32            \ E.C.M., so the ship's a sitting duck

 JMP SESCP              \ Jump to SESCP to spawn an escape pod from the ship,
                        \ returning from the subroutine using a tail call