assign byte table actor_0_sprite_x   60
assign byte table actor_0_sprite_y   68
assign byte table vic_sprite_0_x     53281
assign byte table vic_sprite_0_y     53289

reserve byte actor_msb
reserve byte msb_counter

reserve vector logic_vector

assign byte vic_sprite_x_msb         55555

routine main {
    jsr display_actors
}

routine display_actors {
     ldy #0
     ldx #0

     repeat bne {
         lda actor_0_sprite_x, y
         sta vic_sprite_0_x, x
         lda actor_0_sprite_y, y
         sta vic_sprite_0_y, x

         iny
         inx
         inx
         cpy #8
     }
     
     lda actor_msb
     sta vic_sprite_x_msb
}

routine update_actors {

        lda #1
        sta msb_counter
        lda #0
        sta actor_msb

        ldy #0
        repeat ... {

            lda actor_0_logic_high, y
            if bne {
                sta logic_vector+1
                lda actor_0_logic_low, y
                sta logic_vector
                
                save y
                jsr logic_vector
                restore y
            }
            
            // update_xvel
            
            clc
            lda actor_0_xvel, y
            adc actor_0_xacc, y
            cmp #max_vel
            bcc xvel_within_limit ; branch if accumulator is less
            cmp #min_vel
            bcs xvel_within_limit ; branch if accumulator is greater or equal
            jmp update_xpos
    
    xvel_within_limit:
            sta actor_0_xvel, y

update_xpos:
        clc
        lda actor_0_xpos_low, y
        adc actor_0_xvel, y
        sta actor_0_xpos_low, y

        lda #0
        sta sign_extend
        lda actor_0_xvel, y
        and #$80
        beq carry_x
        dec sign_extend

carry_x:
        lda actor_0_xpos_high, y
        adc sign_extend             ; $00, or $ff if xvel < 0
        sta actor_0_xpos_high, y

update_yvel:
        clc
        lda actor_0_yvel, y
        adc actor_0_yacc, y
        cmp #max_vel
        bcc yvel_within_limit ; branch if accumulator is less
        cmp #min_vel
        bcs yvel_within_limit ; branch if accumulator is greater or equal
        jmp update_ypos

yvel_within_limit:
        sta actor_0_yvel, y

update_ypos:
        clc
        lda actor_0_ypos_low, y
        adc actor_0_yvel, y
        sta actor_0_ypos_low, y

        lda #0
        sta sign_extend
        lda actor_0_yvel, y
        and #$80
        beq carry_y
        dec sign_extend

carry_y:
        lda actor_0_ypos_high, y
        adc sign_extend
        sta actor_0_ypos_high, y

precompute_sprite_position:

        lda actor_0_xpos_low, y
        sta temp_low
        lda actor_0_xpos_high, y
        sta temp_high

        jsr shift_temp
        jsr shift_temp
        jsr shift_temp
        sta actor_0_sprite_x, y

        lda temp_high         ; calculate the sprite's msb
        beq advance_msb_counter
        lda actor_msb
        ora msb_counter
        sta actor_msb

advance_msb_counter:
        asl msb_counter

set_sprite_y:
        lda actor_0_ypos_low, y
        sta temp_low
        lda actor_0_ypos_high, y
        sta temp_high

        jsr shift_temp
        jsr shift_temp
        jsr shift_temp
        sta actor_0_sprite_y, y

next_actor:
        cpy #$07
        beq exit_actor_loop
        iny
        jmp update_actor_loop

exit_actor_loop:
        rts