Change NMI to use only necessary, the rest in mainloop

src/spaceship.asm

@@ -9,35 +9,43 @@
 .import read_controller
 
 .proc nmi_handler
+
+  PHP
+  PHA
+  TXA
+  PHA
+  TYA
+  PHA
+
+  ; copy sprite data to OAM
   LDA #$00
   STA OAMADDR
   LDA #$02
   STA OAMDMA
 
-  ;Update tiles *after* DMA transfer
+  ; set PPUCTRL
-  JSR update_player
+  LDA ppuctrl_settings
-  JSR draw_player
-  JSR read_controller
-
-
-  LDA scroll
-  CMP #$00
-  BNE set_scroll_positions
-
-  LDA ppucrtl_settings
-  EOR #%00000010
-  STA ppucrtl_settings
   STA PPUCTRL
-  LDA #240
-  STA scroll
 
-set_scroll_positions:
+  ; set scroll values
-  LDA #$00
+  LDA #$00 ; X scroll first
   STA PPUSCROLL
-  DEC scroll
   LDA scroll
   STA PPUSCROLL
 
+  ; all done
+  LDA #$00
+  STA sleeping
+
+  LDA#$00
+  STA sleeping
+  
+  PLA
+  TAY
+  PLA
+  TAX
+  PLA
+  PLP
   RTI
 .endproc
 
@@ -160,9 +168,6 @@ done_checking:
 .export main
 .proc main
 
-  LDA #239
-  STA scroll
-
   LDX PPUSTATUS
   LDX #$3f
   STX PPUADDR
@@ -236,7 +241,7 @@ insideloop2:
   BNE outsideloop2
 
   LDA #%10010000
-  STA ppucrtl_settings
+  STA ppuctrl_settings
   STA PPUCTRL
 
 vblankwait: ; wait for another vblank before continuing
@@ -247,8 +252,34 @@ vblankwait: ; wait for another vblank before continuing
   STA PPUCTRL
   LDA #%00011110 ; turn on screen
   STA PPUMASK
-forever:
+
-  JMP forever
+mainloop:
+  ;Update tiles *after* DMA transfer
+  JSR update_player
+  JSR draw_player
+  JSR read_controller
+
+  ; Check if PPUCTRL needs to change
+  LDA scroll ; did we reach the end of a nametable?
+  BNE update_scroll
+  ; if yes,
+  ; Update base nametable
+  LDA ppuctrl_settings
+  EOR #%00000010 ; flip bit 1 to its opposite
+  STA ppuctrl_settings
+  ; Reset scroll to 240
+  LDA #240
+  STA scroll
+update_scroll:
+  DEC scroll
+
+  ; Done processing; wait for next Vblank
+  INC sleeping
+sleep:
+  LDA sleeping
+  BNE sleep
+
+  JMP mainloop
 .endproc
 
 .segment "ZEROPAGE"
@@ -257,11 +288,30 @@ player_y: .res 1
 pointerLo: .res 1
 pointerHi: .res 1
 scroll: .res 1
-ppucrtl_settings: .res 1
+ppuctrl_settings: .res 1
 pad1: .res 1
 .exportzp player_x, player_y
 .exportzp pad1
 
+sleeping: .res 1
+
+NUM_ENEMIES = 5
+; enemy object pool
+enemy_x_pos: .res NUM_ENEMIES
+enemy_y_pos: .res NUM_ENEMIES
+enemy_x_vels: .res NUM_ENEMIES
+enemy_y_vels: .res NUM_ENEMIES
+enemy_flags: .res NUM_ENEMIES
+
+; player bullet pool
+bullet_xs: .res 3
+bullet_ys: .res 3
+
+;export all pools
+.exportzp enemy_x_pos, enemy_y_pos
+.exportzp enemy_x_vels, enemy_y_vels
+.exportzp enemy_flags
+
 .segment "RODATA"
 palettes: .incbin "background.pal"