[fstarred]

Ok, this is my updated code

;*****************
;*   Constants   *
;*****************

OldOpenLibrary    = -$198        ; -408
CloseLibrary    = -$19E        ; -414

DMASET=    %1000000111000000
;     -----a-bcdefghij

;    a: Blitter Nasty
;    b: Bitplane DMA (if this isn't set, sprites disappear!)
;    c: Copper DMA
;    d: Blitter DMA
;    e: Sprite DMA
;    f: Disk DMA
;    g-j: Audio 3-0 DMA

    SECTION    CODESECTION,CODE    ; This command will run the below code
                    ; on FAST RAM (if enough) or CHIP RAM

START:
    MOVE.L    $4.W,A6            ; Exec pointer to A6
    LEA.L    GfxName(PC),A1        ; Set library pointer to A1
    MOVEQ    #0,D0
    JSR    OldOpenLibrary(A6)    ; Open graphics.library
                    ; write to D0 the offset
    MOVE.L    D0,A1            ; Use Base-pointer
    MOVE.L    $26(A1),OLDCOP        ; Store copperlist system address,
                    ; retrieved $26 from glib offset
    JSR    CloseLibrary(A6)    ; Close graphics library    
                
    move.l    #COPPERLIST,$dff080    ; COP1LC - Point to #COPPERLIST
    move.w    d0,$dff088        ; COPJMP1 - Start COP

main:
    cmpi.b    #$ff,$dff006    ; VHPOSR wait for horizontal line
                ; of the light pen
    bne.s    main        ; if pen did not reach the end, repeat loop
    bsr.s    movebar        ; 

waitframe:
    cmpi.b    #$ff,$dff006
    beq.s    waitframe

waitmouse:
    btst    #6,$bfe001    ; check for left mouse button
    bne.s    main        ; if not, repeat the above line

end:
    move.l    OldCop(PC),$dff080    ; COP1LC - Point to default COP system
    move.w    d0,$dff088        ; COPJMP1 - Restart COP

    move.l    4.w,a6
    jsr    -$7e(a6)    ; Enable  Multitasking
    move.l    gfxbase(PC),a1    ; Point to gfxbase
    jsr    -$19e(a6)    ; Closelibrary
    rts

GfxName:
    dc.b    "graphics.library",0,0
    
GfxBase:        ; Dedicated to offset "graphics.library"
    dc.l    0     

OldCop:            ; Dedicated to system COP address
    dc.l    0


Movebar:
    LEA    REDBAR,a0
    TST.B    Direction
    BEQ.S    Movebardown
    BNE.S    Movebarup
    RTS

SwitchDirection:
    BCHG    #0,Direction
    RTS

Movebarup:
    SUBQ.B    #1,8(a0)
    SUBQ.B    #1,(a0)
    CMPI.W    #$2c07,(a0)    ; Upper limit
    BEQ.S    SwitchDirection
    RTS    

Movebardown:
    ADDQ.B    #1,(a0)
    ADDQ.B    #1,8(a0)
    CMPI.w    #$2b07,8(a0)    ; Bottom limit
    BEQ.S    SwitchDirection
    RTS    

Direction:
    DC.B    0,0    ; direction flag

    SECTION    GRAPHIC,DATA_C    ; Section below MUST be executen on CHIP RAM,
                ; because COPPERLIST requires it
        
COPPERLIST:
    dc.w    $100, $200    ; BPLCON0 - THE BITLANE CONTROL
    dc.w    $180, $000    ; Color 0 - BLACK
    dc.w    $2c07,$fffe
    dc.w    $180, $0f0
    dc.w    $2d07,$fffe
    dc.w    $180, $000    ; Color 0 - BLACK
    

REDBAR:
    dc.w    $ab07,$ff00    ; Wait for line $7f (half screen)
    dc.w    $180, $F00    ; Color 0 - RED
    dc.w    $ac07,$ff00    ; Wait for line $80 (next line)

    dc.w    $180, $000
    dc.w    $ffdf,$fffe

    dc.w    $2c07,$fffe
    dc.w    $180, $0f0
    dc.w    $2d07,$fffe

    dc.w    $180, $000    ; Color 0 - BLACK
    dc.w    $FFFF,$FFFE    ; END OF COPPERLIST

Can you give me some help to show the red bar reaching the bottom part of the screen (touch the green bar)?

Thank you so much for your code and hints !!!

Edit:

Thanks to photon explanation,
I think I can work on it, once I have some time free I'LL post an update