The ApplyTactics (Part 3 of 8) subroutine - The Sentinel on the BBC Micro

       Name: ApplyTactics (Part 3 of 8)                              [Show more]
       Type: Subroutine
   Category: Gameplay
    Summary: If the enemy has any residual energy, try expending it onto the
             landscape in the form of a tree (and end tactics if successful)
    Context: See this subroutine in context in the source code
 References: No direct references to this subroutine in this source file


.tact6

 STX viewingObject      \ Set the viewing object to the enemy we are processing,
                        \ so everything is done from their viewpoint from now on

 JSR ExpendEnemyEnergy  \ Drain one unit of energy from the enemy and expend it
                        \ onto the landscape by spawning a tree, if possible
                        \
                        \ This ensures that if an enemy has absorbed energy from
                        \ somewhere, it always dissipates back into the
                        \ landscape it when it gets the chance
                        \
                        \ If we can't spawn a tree because we are about to pan
                        \ the screen and the tree would spawn in a position that
                        \ would be visible on-screen, then the routine does not
                        \ expend energy or spawn a tree, and instead it gives up
                        \ and aborts applying tactics for this gameplay loop
                        \
                        \ If we successfully spawned a tree then the object
                        \ number of the tree is in X

 BCS tact7              \ If the call to ExpendEnemyEnergy returned with the C
                        \ flag set, then either the enemy didn't have any energy
                        \ to expend or we couldn't spawn a tree, so jump to part
                        \ 4 to keep applying tactics

 JMP tact25             \ Otherwise that's enough tactics for this iteration, so
                        \ jump to tact25 with X set to the object number of
                        \ the tree to update it on-screen with a dithered effect
                        \ and return from the subroutine using a tail call

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Subroutine ExpendEnemyEnergy (category: Gameplay)

Drain one unit of energy from an enemy and expend it onto the landscape by spawning a tree, if possible

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Entry point tact25 in subroutine ApplyTactics (Part 8 of 8) (category: Gameplay)

Dither the updated object #X onto the screen, with bit 7 of drawLandscape determining whether the object is drawn on its own (bit 7 set) or with the surrounding landscape (bit 7 clear)

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Label tact7 in subroutine ApplyTactics (Part 4 of 8)

[X]

Variable viewingObject in workspace Zero page

The number of the viewing object

Gameplay: ApplyTactics (Part 3 of 8)