Main loop: MainLoop (Part 5 of 15)

       Name: MainLoop (Part 5 of 15)                                 [Show more]
       Type: Subroutine
   Category: Main loop
    Summary: Update lines, check flying skills, increment main loop counter,
             update the radar
  Deep dive: Program flow of the main game loop
    Context: See this subroutine in context in the source code
 References: No direct references to this subroutine in this source file


.main6

 JSR UpdateLinesToShow  \ Update the linesToShow list, moving any lines that
                        \ aren't visible into the linesToHide list

 JSR ExplodeAlien       \ If an alien has been hit, process its explosion, with
                        \ all the convulsions that entails

 LDY #2                 \ Check to see if we are flying under the suspension
 JSR CheckFlyingSkills  \ bridge and award points if we are

 LDY #34                \ Check to see if we are flying down the main street of
 JSR CheckFlyingSkills  \ Acornsville and award points if we are

 INC mainLoopCounter    \ Increment the main loop counter

 LDA mainLoopCounter    \ If (loop counter + 4) mod 8 <> 0, jump to main7, so
 CLC                    \ we only do the following once every 8 iterations of
 ADC #4                 \ the main loop, when the loop counter is 4, 12, 20 and
 AND #7                 \ so on
 BNE main7

 LDY #1                 \ Update the runway on the radar
 JSR UpdateRadarBlip

 LDX alienToMove        \ Set X to the number of the alien whose turn it is to
                        \ move towards Acornsville in this iteration of the main
                        \ loop, which we set in UpdateAliens

 BMI main7              \ If X is negative, then there is no alien to move, so
                        \ jump to main7 to skip the following

 LDY #33                \ Set Y = 33 so the call to UpdateRadarBlip updates the
                        \ alien on the radar

 LDA alienState,X       \ If the moving alien's state is < 27, skip the
 CMP #27                \ following instruction as the alien is not flying
 BCC main7

 JSR UpdateRadarBlip    \ The moving alien's state is >= 27, which means it is
                        \ either flying to Acornsville or is in the final
                        \ descent stage, so update the alien on the radar