MainLoop example

MainLoop
        moveq   #0,d0               ; clear d0
        move.w  game_state,d0       ; get game state on d0
        add.w   d0,d0               ; multiply ID by 2 (if d0 = 1 -> d0 = 2)
        add.w   d0,d0               ; multiply previous by 2 (if d0 = 2 -> d0 = 4)
        jsr     @index(pc,d0.w)     ; jump to @index addr + d0
        bra     MainLoop
@index:
        bra.w   TitleScreen_Init    ; (0) each bra is 4 bytes long
        bra.w   TitleScreen         ; (1) each bra is 4 bytes long
        bra.w   GameMode_Init       ; (2)
        bra.w   GameMode            ; (3)

TitleScreen_Init:
        ; <Initialization, plane loading, etc>
        move.w  #1,game_state       ; change game state
        rts                         ; load it

TitleScreen:
        ; "main" status...
        move.w  #2,game_state       ; change game state
        rts                         ; load it

GameMode_Init:
        ; <Initialization, plane loading, etc>
        move.w  #3,game_state       ; change game state
        rts                         ; load it

GameMode:
        ; "main" status...
        ; (...)